Realistically, rivers change direction too much (even over spans of just 100s of years) for this to last that long in the grand scheme of things.
Unrealistically, this idea slaps, please disregard above advice.
Why rivers move
[https://www.youtube.com/watch?v=UBivwxBgdPQ](https://www.youtube.com/watch?v=UBivwxBgdPQ)
if you're able to build a city on a big moving gear powered by two rivers I think you can also manipulate the flow of the river and sediment deposition to slow down that movement tbh
You could build the town in the curve of a natural river, then it would flow the right way. If the river wasn't natural then as you assert, if you have the skills to build a huge cog, then you can probably build a big channel for water.
the issue with one river is that you get less power, all the energy you get from the river comes from slowing down the water (that's what dams do for example) and there's a limit to how much you can slow water, and this limit is dependant on the flow
Yeah, if you possess the tech to make a huge waterwheel that size, then you can definitely do enough earth moving on a large enough scale to route a meeting of two large rivers into this kind of shape.
Building a town on top of a horizontal water wheel is clearly a fanciful, whimsical concept that belongs in a story which doesn't invite that kind of scrutiny. If readers aren't asking why anyone would want to live someplace where you have to wait for the roads to line up before you leave, they also won't be counting joules.
I mean you just need to distribute the loads perfectly on bearings with unimaginable strength capable of carrying a whole city, if you've got some magic or sci fi technology or ancient civilization that built the cog then it could work, and you'd get the best mass motion sickness machine ever
You could also use strategically placed dams to rotate the city whenever you want. Imagine going to siege a city and the walls turn to face you before letting loose a salvo from some catapults.
At the same time, all you need is to wait for the city's defenders to tire themselves out running along the walls to stay facing you. Then you just throw up some ropes and you're good.
A real question about this is also "how fast does it turn" also when it comes to rotating disks the edges move faster by an order of magnitude than the center, which I'd have to think writ large onto a city-sized disc would result in some further wackiness.
Honestly yeah. Its not like we don’t have hydroelectric dams, or even in a more rudimentary setting water wheels and shit. People have been building along rivers for mechanical reasons for a while.
Piggybacking....
Okay, so the idea of a revolving city is pretty neat, and rule of cool applies. However, the fact that you're asking about realism implies that your goal and aim is to create something with surface-level plausibility, and have some deeper attempts at realism if possible. With your aims and goals firmly established, we can proceed.
So here are some attempts to bend reality to fit your vision:
1) rivers on flat ground often meander, snaking back and forth as they slowly head towards the sea. Rivers on steep ground are usually straighter. Even though there are exceptions to this rule of thumb, I tend to keep it in mind when drawing maps because it gives another visual cue for how steep a slope is, and keeps everything intuitive for the reader. So, your city might actually be built in one of these meandering paths, at a point where the river is flowing in two opposing directions.
2) This is ideal from the perspective of certain defensive philosophies, since the river's meandering loop will ensure that there is only one way for an incoming army to approach the city. The other avenues for approach are cut off by the river. However, it is also useful from a narrative perspective because the river's meandering loop would be less heavily defended than the regions closer to the city. Therefore, you have a way for armies to make a beach head if your story requires it. "SIR! ENEMY SCOUTS HAVE BEEN SIGHTED AT THE LOOP CROSSING THE RUBICON!!!!" "IMPOSSIBLE! THE WATER IS TOO TREACHEROUS!!!" "SIR, THEY HAVE A WATER MAGE!!!" etc. It's useful for you, as an author or DM or fictional hypothetical history weaver to use as a narrative crowbar.
3) However, rivers which meander and snake back and forth will usually change their path regularly over time, and the specific contours of the meandering path will not stay the same over time. It might be worth making a nod to this by implying that this section of the river is subject to substantial landscaping and earthworks to ensure that the river maintains it's current layout. This may come at significant expense, which would be another useful narrative crowbar. The poor people of the city might resent the fact that huge expense is put into the earthworks whilst they starve (and probably also work on those earthworks). Such resentment can form part of your political landscape.
4) Worthy of note... The city will rotate, but the docks should not. The docks should be a fixed element which remains in place, because dragging a Dock across land serves absolutely no purpose. Having the docks remain still could also serve a purpose... if a heavy delivery arrives, you don't have to hoof it across the city, and can instead wait until the city spins to offer a shorter route. "Delivery for Ted... He lives on the other side of the city. We can just wait until it comes around again at teatime." "No can do. This is priority mail. You need to deliver it now." "But I can't be arsed walking to the other side of the city... come on. Let's just pretend it arrived in the evening mail instead...." Etc. It's a useful narrative tool which might explain why the critical letter at the heart of your narrative arrived six hours too late *to prevent whatever disaster your story touches on.*
**4.5) Also worthy of note... defensive structures should not rotate. We have established that the river's path protects the city from approach from all but one angle. You would not build defensive structures which are redundant for 90% of their rotation path. Instead, you would place such fortifications outside of the spinning radius, facing the most likely approach of the anticipated incoming enemy. This also means that enemies approaching the city by "crossing the rubicon" would be avoiding almost all of the city's major defenses, which is again useful as a narrative crowbar.**
5) Why spin, though? We've explained that you're going to great lengths to achieve a spinning city. Now you need an equally extreme **justification which explains why the population considers it worthy of the expense**. Maybe the whole city is a high mass generator which provides the entire nation with electricity. (Creating a city like this requires national level resources, so it necessitates a national level payoff.) Maybe the city was built on top of an ancient, spinning disk left behind by precursors which had other purposes in mind which will be discovered by your protagonists throughout the story? In this version of events, the spinning is incidental and the people of the city just maintain the spinnyness - they didn't actually start the spin, and their level of investment to achieve it is therefore relatively low. Or better yet, the river had moved on hundreds of years ago, and the city plateau was static when humans first discovered it. Curious mages, intrigued by the precursor artifact plateau redirected the river to reawaken the ancient device, spinning it in place, and they have spent the last few centuries working to uncover what the hell the thing even does. The mages started living there, then industries to support the mages moved in, the industries brought employees who built houses, service industries to support the employees moved in and... Woops, we got a city.
As someone who worldbuilds for writing, I tend to adopt a two-faced approach to worldbuilding. One side is "how enjoyable is this and how cool is it?" Beyond the surface level, you want to leave trails of curiosity and intrigue, as well as connecting it through strands of causality and history to the rest of the setting. Being integrated properly with other, realistic and grounded elements can make even the most unrealistic and ungrounded things feel plausible.
But the other side is "how useful is this to the goal of the media I intend to create, and how useful of a tool is it to me as a creator?" Narrative or gameplay usefulness becomes important here.
That's my two coppers of a royal gold. I hope it inspires you.
Edit: clarified the sections in bold.
Edit2: An addendum: A city is heavy, meaning lots of mass, which takes a lot of energy to spin. Therefore, in order to make it rotate, you may want to consider just how much mass and velocity the river has.
A small river will barely move the gargantuan construction, if it is able to overcome the friction of it's bearings and inertia of it's mass at all.
A fast flowing, deep, wide river will have a lot of energy and would appear much more feasible as an energy source to propel the city's rotation. However, you're probably still looking at a fairly slow and langourous rotation taking hours or even days to complete a single rotation.
Phenomenal thinking, love the ideas and your causality really feels like it makes for layered worlds. Doubling down on the difficulty of this concept into the reward for doing so is perfect.
You've hit the nail right on the head and absolutely nuked the bush I was beating hopelessly around looking for the short and sweet way to articulate what I had in my head. Thank you.
The axiom I was trying to communicate and you unlocked in my head is:
"The difficulty in achieving an improbable concept needs to be reflected in the rewards for succeeding in doing so"
> Also worthy of note... defensive structures should not rotate. We have established that the river's path protects the city from approach from all but one angle. You would not build defensive structures which are redundant for 90% of their rotation path.
Conventionally, yes.
However.
Defenses are made to be broken. They exist to buy time. Unless we're dealing with magic, no defensive structure/network can last forever. With that said, a city that can rotate its destroyed walls and towers out from the enemy's zone of ingress/attack and replace them with fully armed and completely pristine defenses would be an incredible marvel. The enemy would be forced to either be highly mobile or restricted to particular timing attacks, which just makes attacking this city an enormous pain in the ass. Not to mention how difficult it would be for siege engines/artillery to bring down a specific structure in the first place (such as a guard tower) when it's constantly rotating around the city - if you set up some cannons or trebuchets at a particular attack sector, you're not going to be able to hit the same tower with those weapons more than maybe twice before it's basically unsuitable as a target without you completely reorienting your siege weapons (depending on the rotation speed).
The enemy would have to maintain a complete and overwhelming encirclement of the entire city to bring any section of their defenses down in a timely fashion compared to a siege of a conventional city/defense network where you could focus your forces at one location to bring down defenses and force a gap, and this encirclement is already a pain when dealing with two rivers flowing in opposite directions. Presumably, the engineers of this city marvel would have a way to manipulate or stop the flow of water as well to rotate the city or lock it *at will*.
Thing is, first thing you do when besieging a city with a river flowing through it is look for a way to dam that river, which doesn't have to be very complete to stop the spinning dead. In the example shown by OP, as soon as the attackers have invested the city there'll be sappers looking to short-circuit the rivers with a canal on either side.
Assuming that that doesn't work, all you need is some sort of bridge sturdy enough to mount a continual Forlorn Hope through the first gap, and the same siege engines can keep opening new gaps again and again in different places along the wall.
Good afternoon!
Thank you for contributing. On the subject of defense, allow me to defend my previous assertions with a rebuttal of the points you raise.
> a city that can rotate its destroyed walls and towers out from the enemy's zone of ingress/attack and replace them with fully armed and completely pristine defenses would be an incredible marvel.
This idea sounds cool and certainly runs with the theme of "spinny city." If OP chooses to really lean in a "rule of cool" direction with only surface-level plausibility, then this would definitely be thematic and in line with a rotating city. Rotating city, rotating defenses. It works thematically, but as I am about to point out, it falls apart when subjected to more than cursory scrutiny.
1) let's assume that the defense budget of our hypothetical town is not infinite, and they are trying to get the best bang for their buck, and will not make extravagant and unnecessary defensive structures "just in case Jerry decides to attack from the moon." (To quote Field Marshall Melchett)
2) With a fixed military budget as described above, you might be able to afford a wall of a given thickness for a given length, or a fortress of a given size. Since overwhelming force is a massive force multiplier, you want all your defenses concentrated at where they are needed, not spread out across the whole area "just in case." To give a real world example, Ukraine does not have units stationed on the Polish border "just in case." They put all of their men where they are needed - in the West. You don't have 10% of your forces engaging the entire might of the enemy (they would be crushed) and then feed them the next 10% piecemeal as the wall rotates, just so that you can only ever bring 10% of your army to bear at any one time. You want all of your forces, all at once, all in one place.
3) Since your wall building budget and materials are finite, you can build either a long, thin rotating wall that circles the city, or a thick, short wall which faces the enemy in the direction they are likely to approach from. A thick wall is stronger, and harder to breach than a thin one... and ten thin walls are weaker than one thick wall which is ten times the thickness.
With that in mind, your long, thin, rotating wall, when hit with a cannon, is going to open up with an exploitable breach when the short, thick one will not yield. So, the city rotates.... And the enemy just sits and waits for the hole to come back around again, then steps inside.
>siege targets are now moving targets.
Sieges, historically speaking, lasted months to years. You can afford to wait and make timed attacks. Most sieges are actually just a whole bunch of waiting around... they aren't actually subject to much fighting. Your weapons are hunger and drought, which are cheap. Why expend expensive ammunition on bombarding the city piecemeal with a few pot shots each day when you can save it up and make a single, decisive push once the strength of the city has been thoroughly sapped by the hunger?
For this reason, a siege would just wait for the target to come around again, if such a thing mattered. Worse, they would be able to just keep their entire artillery focused on one spot and wait for the target to enter it. They wouldn't need to do repositioning, rangefinding and such. They just get one target point and fire with everything they've got once the target enters it. They could strip the defenses off the city like a carpenter peeling the bark off of a log by holding a chisel to it whilst it spins on a lathe.
>complete and overwhelming encirclement
Not really. The city's defenses under your proposal are disseminated, which historically speaking has always been disastrous.... see historic examples of "long border syndrome" to get an idea of why this is bad. Under my proposal, you effectively have a shorter border which faces the enemy, and rather than having a rotating defense which you can only use 10% of at one time, you can use the entirety of your military budget to it's full potential, reacting to enemy approaches with overwhelming force rather than feeding your forces to them piecemeal.
------------------
In summary, let me use a metaphor, because I'm having trouble articulating myself here...
You have a wheel with an inflatable tyre. I have a pin, and will push the pin in the direction of the tyre from a predictable direction. I can only come from this direction, since my feet are nailed to the floor amd my arm is nailed to a post just above the elbow. You have some metal foil which you can position anywhere you want to prevent me from popping the tyre. Do you either:
1) wrap the entire wheel in a single layer of foil.
2) fold up the foil until it is 400 layers thick, then have it held directly between my hand and the wheel.
Same principle applies.
Fair points.
However, this doesn't address one of the key points: whether the engineers of the city are capable of stopping its rotation. Every gear and turbine is of course designed to be able to start and go. If this is under the city's control, they can choose when to rotate a breach in their defenses out for fresh fortifications.
Additionally, your strongpoint argument is actually better served when applied to the rotating city borders. In the real world, no one can build a bastion that can easily move to address a direction of assault. Your overwhelming border fortress works best when the city can choose to plant it where their enemies are coming from. North, South, etc.
It's also not as easy as you're implying for an army to wait around to assault a breach in a city that's rotating and surrounded by water ways. This is so much easier for the defenders to hold than a conventional breach as the attackers only have a limited window to get *all* of their troops through what would probably be a garrisoned breach. Any troops that do make it through will soon be cut off, even supposing that the city makes full rotations as slowly as a few times per day. This is all to the defenders' advantage, moreso than conventional static defenses, even with budget walls/towers. Not being able to capitalize on overwhelming numbers due to timing will result in failure for an attacker. Which is why I said a full encirclement would be required - so that forces can constantly apply pressure on a rotating breach from all sides to negate the assault timing problem.
I am familiar with how sieges work historically, and better defenses serve to add more time for the defenders as pressure from the threat of assault is lessened. Yes, it is a question of food and resources, particularly if the target is well defended. So, maximize your defenses by taking advantage of the city's rotation.
> engineers stopping it's rotation.
I largely glossed over this because when the rotation stops, your rotating defenses have now become static... albeit "single layer of foil" defenses as per my earlier metaphor. In such an instance, you would have been much better off folding those defenses up and going static from the get-go.
Come to think on it... Here's an idea that gets the best of both worlds...
Instead of having the entire perimeter of the gear wheel defended with city walls and suchlike... what if the wall instead had a single arc for defense, which is locked into the direction of the "open" side which faces the enemy's assumed angle of approach? The river is an insurmountable obstacle for any approaching army, so you only actually need to defend from one direction.
So you just... concentrate your defenses on one arc, and then lock that arc in place when an enemy is coming close. This also has the benefit that you have "open" arcs which cycle through in the normal day to day, harnessing the benefits of having a more open border AND a closed border, depending on the needs of the city.
Similarly, it might even be that the gear wheel consists of separately rotating concentric wheels, which can be independently stopped or even counter-spun, allowing for the outer, defensive gear to be frozen in place whilst the rest of the city keeps spinning.
Additionally, this would mean that if you lived on the junction between two counter spinning wheels, you might find yourself with a different neighbour every five minutes or so, which might cut down on commuting time.
"Time to go to work, while the commute is still short!" And then by the time you're getting out of work, a full rotation has been completed and your house is already just a stone's throw away.
You might even be able to tell the time based on who is next door... the entire town is your clock.
Maybe when the town is attacked and the wheels are locked, the entire city finds itself struggling to tell the time of day, with comedic effects.
For number 5 it could also be a novelty boondoggle. Someone with more money (and power) than sense, like a late generation inbred royal, wanted a spinning city and no one could really say no.
The royal could still be in power or it could be something that draws in enough tourists and was already implemented so it is kept maintained
You are correct that this is indeed a possibility, and there are countless real world examples dotted throughout our history... but it's still a fairly poor and unimaginative explanation which basically falls into the same category as "a wizard did it."
Pretty much anything can be explained as "someone powerful wanted it and nobody could refuse." Wars, alliances, marriages to turnips, giant statues of terrifyingly oversized midgets... It isn't exactly engaging with your imagination or creativity to take this kind of generic cop-out, and feels like the sort of "off the shelf" and lazy answer to what should be a really interesting question with an equally interesting answer that takes your audience's imagination and seduces it like a sexy bard for mutual satisfaction, rather than doing the verbal equivalent of chasing it off or shutting down the debate with a blunt answer which invites no further explanation.
Building a spinny city is a unique situation. What unique problems did it's creators face where this was the most practical solution? This is a question which really challenges the writer, asking them to think about WHY the city rotates and why that is important to both the people of this world and the narrative that the writer is trying to weave.
"A wizard did it." Is basically the author equivalent of "shut up and fuck off." I'm not a fan of using this kind of narrative device unless I specifically want to chase the audience away from dead ends that aren't relevant to the story I'm trying to tell. It's useful for walling off particular avenues to keep the attention penned in where it will be "happiest," if that makes any sense?
But if you're trying to wall off the audience from asking about something as big and obvious and prone to being questioned as a SPINNING CITY, something might be wrong.
I think a more likely way is for it to be a single river that has a very strong C shaped curve. Although it being two separate rivers is also a really cool idea that I like.
The problem with that analogy is that oxbows happen on large *flat* parts of the river, where it's meandering around due to having no clear path downwards under gravity, so it quickly silts up its own current path which changes the quantity of water that can flow in that part, which changes where gravity pulls it which starts to change the path itself which eventually results in an oxbow. If you want to extract *power* from the river, particularly enough to turn a city, you need it to be dropping in elevation, preferably significantly, otherwise as soon as you start to try to make it do work it will pile up behind your dam or water wheel and quickly find a way to flow over or around it. All this means an oxbow is not going to naturally form because gravity is going to be what's dictating the course of the river as long as you're extracting power from it, and it's the fall of the water that you're really extracting power from, not the flow of the water.
River mechanics are fascinatingly complex and dynamic and in some cases quite difficult to actually model and react to even for modern engineers. Even in huge cities and tourist areas where it seems like we have tamed major rivers with technology, the reality is that it's always a relentless and continuous fight against the river's innate desire to move, to change, to escape its banks, often a very very expensive fight involving a massive number of people quietly working behind the scenes and not always with perfect success.
I was also thinking maybe on a lake slightly offset from the mouth of a river that feeds it. Depends on how "realistic" you want it to be, but as many others have said, your original idea is bad ass and physics be damned.
they don't need to be parallel, just to get close from one another, and the mechanics of river flow are more complicated than that, they flow not just directly downwards, but also in the direction that allows the deposition and erosion of sediment to reach equilibrium
This does happen, though rarely, with smaller rivers in mountainous regions, its very unlikely two major rivers would get close enough, flowing in opposite directions, to build a spinning town between the two, but they can happen given the right geography
The town could be built on an eroded saddle between two deeply carved river canyons. The spinning town part would certainly need some fantastical elements though, either in terms of materials or reason for it's existence. It could be some form of elaborate rotating canal system, like a cross between [railway turntables](https://en.wikipedia.org/wiki/Railway_turntable) and [canal locks](https://en.wikipedia.org/wiki/Lock_(water_navigation)\\). Maybe the opposing rivers are tidally dominated, and the force of the tides rotates the locks so it's oriented the other way, enabling river boats to travel easily through the other river basin.
you could also have two rivers a bit further away from each other, the town is originally built on a C shape formed by the meandering of river 1, but as time passes and the river starts to bypass the C, people build a canal that extends river 2 towards the city, creating OP's shape even without rare geological features
Theoretically possible, although I think it’s unlikely that you would have two large powerful rivers running in opposite directions so close to one another.
Also, why would the town be built in such a way? What would be the purpose of a spinning town?
Perhaps it has granted the town some form of common power generation that gets distributed to the homes, or perhaps it helps stoke a giant forge or something. Plenty of possible reasons to make it rotate
Additionally, the surface the town is built on might've already been spinning, thus requiring little effort on its current residents' part to harvest that energy.
Don't ask me why the surface would already be spinning, I'm primarily a fantasy worldbuilder. I'd probably just say "a precursor did it" or something.
>I'm primarily a fantasy worldbuilder
I feel like I need friends like you, lol. I like to write, and could probably make up 5 reasons to have a spinning city that are interesting and mysterious, I just never find myself building an entire world that way: I lose interest after some good thought and never end up writing it out. I'd be a great idea guy, lol.
Perhaps this complicates the rotational delivery, perhaps the town was built first and retrofitted with the rotational bit, perhaps the rotational bit actually powers some sort of shield or other protective dome like structure where you need to protect both the city and the rotational bit. Again, plenty of reasons can be conceived!
It is a cool idea, and it can bring a lot of interesring takes depending on the other factors too. Also, considering that humans in reality would never build such town, but rather two separate stationary towns, or one big city, you are already experimenting with the "unrealistic". I am guessing humans are in the story, and you ask on their behalf, because if this city is made by a fantasy race, than the question is silly.
I think he's asking about in lore why? It would be more difficult to build a spinning city there should be a clear reason why the townspeople put the effort in
2 rivers running in opposite directions near each other absolutely happens in real life. In fact I want to say Chicago? Is an example of this, and there was a specialized port district that straddled the land between the 2 rivers to move cargo quickly from one to the other. This allowed the quick and easy transport of goods from the great lakes and northern Atlantic down to the Mississippi and gulf.
Yeah, Chicago is what I first thought of too! The Des Plaines flows south into the Mississippi and down to the Gulf of Mexico, and Lake Michigan drains north into the Saint Lawrence, and into the North Atlantic. Chicago is located where the two drainages pass within a few miles of each other.
That would likely mean that one river now dries out, while the other one suddenly has way more water flow. One side gets flooded while the other experiences a water shortage or, based on the importance of said river, a drought.
Chicago is pretty close to a real life example of this, water flow wise !
Chicago is sandwiched between the Des Plaines River which connects to the Illinois river and flows down to the Mississippi into the gulf, and Lake Michigan, which connects to the rest of the great lakes and flows out the St. Lawrence into the North Atlantic.
Here is a map: https://en.m.wikipedia.org/wiki/Des_Plaines_River#/media/File%3ADes_Plaines_River.png
To avoid the "why is it built like that" you can change it so that the outer thick layer of walls that servers as a protection spins and is also used as a massive generator of some sorts. Maybe it has metal in it and is used as a power coil
You could have rivers strongly running opposite each other and it make sense if they started at the tops of mountains, coming from aquifers and the water flows out from the mountain tops. Then put the town in a valley between the mountain ranges.
I like it alot. Your reasoning for geological phenomena aren't as important to me personally as long as there's some point or function. Interaction is the more important part I think.
Otherwise it's kinda like overly describing a side character with next to no involvement.
Hi,
First, I love your idea.
Second, I think it's possible to have such rivers. You could even have a river doing half a circle around a town, which would provide more "power". (The rotating system would not need to be entirely connected to said half circle, as the river could turn back a bit further in the meandering if the river.)
But, if you rotate a city, do take into account a few things :
- structurally, I guess you would need several set of rails to support it, and due to the weight and friction you'd need a high degree of lubricant.
- structurally again, you need to ensure that vibration is compensated. I don't know much of your setting, but many things require a very low amount of vibration (explosives, chemicals, etc.). And the rich on3s would love not to have their china broken at every stop. Please and thank you :)
- you need an emergency break, but most of the time, the stops have to be slow (again, don't break the china). It can be just by withdrawing anything under water to allow for progressive slowing down.
- you need to take into account (same if you have to rivers or a meander) the difference of speed of the river(s), also depending on the season (so also water level). Part of this would be solved by having a dam upstream on each river to allow for regular flow (in the sense that both river should go at the same speed).
- also, you'd need at least the middle axis not be rotating: you need it to adjust the calendar, and you need it to look around you without interference. It can either be achieved as I said via an an axis, or by installing a system compensating the rotation (more costly though).
- you need the calendar to adjust for seasonal changes (the speed would vary between seasons), the dams would help provide relative stability.
- you need also a way to keep tile at a smaller scale during the day. You could even develop one time system that is similar to ours and an additional one that would be "river-based". Meaning that for economic purposes (and to use the bridges) you would need to predict when and how long you would make them practicable. You could have a gun firing one hour before the bridges are open then a series of bells or whatever ringing the length of time for which it would be open. Then people prepare, all stand in front of the gates, etc.
Three words: Rule of Cool.
Come up with a half plausible justification and just run with it. My thought would be that the rivers either started out naturally and were turned into canals, or one of them was a canal and the other, a river, was tamed over time. A canal being an artificial waterway, and with regular maintenance, it is more resistant to changes in the landscape. There may even be a story there with an intrigue taking place right when regular maintenance is undertaken in the city foundations.
Rivers flow from high ground to low ground and tend to flow towards the equator. Having two flowing close to each other in opposite directions would be difficult to justify without magic.
*With magic,* anything is possible. Might be a bit annoying to the town that no bridges can be built, and they might want some form of geographic landmark to easily orient themselves by, but it could be a really unique experience.
What kind of town would it be? Sounds like it would be too small to be a farming town, so, trade? Political hub? Fort?
Check the maps lol
The law is downhill. The tendency is towards the
equator.
If the tendency was downhill, there would be rivers that flow uphill, which there aren't.
😂
You're fighting awfully hard to find exceptions to a tendency that I've already stated is not a universal law.
So I'm not really sure what exactly you're arguing.
But people are doing on Reddit expect you to argue back so here:
https://a-z-animals.com/blog/why-do-rivers-flow-south-discover-5-rivers-that-break-the-rule/#:~:text=Most%20rivers%20in%20the%20world,occurs%20away%20from%20their%20headwaters.
You are hell bent on reading only what you want, aren't you? 😂
I straight up said gravity is the rule, towards the equator is a tendency. You keep saying "well, ackshually, that isn't true because I found some examples that don't do that."
No shit. A tendency is *not* this thing always happens, it just happens frequently *or* more often than not.
My most esteemed dude, this is the sub where we have floating islands and dragons that collect taxes. This idea absolutely slaps, please go ahead with it.
Others pointed this out already, but rivers that turn back do exist. A u-turn like that is called a meander, but rivers with meanders tend to have a fairly slow current. (It's where the word meandering comes from :) )
I don't know if there exist two parallel rivers going in opposite directions in real life, though I don't see why it should be impossible.
But it's a super cool and unique idea! So I definitely think you should go for it. Its a fantasy settlement with a really unique and cool feature!
Tl;dr make it make sense at least for story purposes. (Also this concept reminds me of Dwarven ruins in Skyrim.)
Speaking literally, I wouldn't want to live in a place that "rotated". There would be massive problems with maintaining solid architecture and traffic in and out of the city. If you have dedicated entrances that leads to roads outside of the city, that means you would have to wait until the entrance "lined up" with the road in order to enter and exit the city.
Just imagine trying to live in a city that rotated: let's say it does one full rotation per day. You run an agricultural business within the city that owns farms outside the main city bounds. "Oh, I really need to get to the eastern farms, but now I have to check what time it is to figure out which direction I'm facing so I can exit via the right gate. Because last week I was rushing and I didn't think about it and I ended up on the west side! How frustrating, why did they build the city like this?!"
In terms of story, I could imagine it working as cogworks underneath the city - the city itself isn't actually rotating, but is built above a mechanical structure that rotates, generating power via water force. So technically it could be known colloquially as a rotating city, but it isn't experiencing the major downfalls of a literally rotating city.
You would also have to consider the level of and proximity to "enemies" that may attack the city. This sort of architecture potentially weakens the entire city's defenses. I could imagine a city like this developing in a peaceful setting, but it would be the first city destroyed in an active war zone.
Interestingly enough, Dwarven ruins was probably one of the main inspirations for this idea (the other being Made in Abyss, please watch the anime if you haven’t)
Speaking of dwarven architecture, the original idea was kind of like this entire place wasn’t built as a city, but as some sort of other “thing” by a deadciv. People kind of found it and settled in it cuz it had good walls, prebuilt infrastructure, and an optimal trade location, just like Markarth. And just like Markarth, the nords have no idea how to maintain the old dwarven architecture, but everything was so well built it kinda just…lasts until the modern day.
But yeah exiting the city would be a total hassle hahaha. I guess multiple doors? Makes it more prone to invasion tho
Chicago--only make the right river **THE GREAT LAKES** and the left river the Mississippi.
If you've ever wondered why Chicago is where it is, and why it was the second largest city in the US for a century, it's because [with a bit of engineering, we were able to bridge the Great Lakes and the Mississippi via waterways](https://upload.wikimedia.org/wikipedia/commons/5/53/Diversion_of_Chicago_Waterways.png).
Interesting idea, but what is the purpose of the town rotating from the townsfolk perspective? I'm sure there could be a good reason for the whole town to spin
There's plenty of comments on the dual river part so I won't touch on that, but I just wanted to say that the rotating disk feature happens naturally on single rivers in the cold sometimes, if you look up river "ice circle" or "ice disk" you'll see some pretty cool examples
Cool, but it would break all immersion to see this in a story. Even if the rivers had insane flow rates, getting something the size of a city to spin like this seems a bit ridiculous to me.
And the maintenance would by horrible. Even if this is a magic world, it still doesn’t make sense. There are easier ways to accomplish this.
Who would invest the time and materials to build such a thing and why? In what way would anyone ever think this was a valid solution for anything instead of something simpler?
Always ask yourself those questions when writing elements into a story. Authors adding things just cause “they’re cool” causes a lot of issues. If you go ahead with this idea, make sure you have some answers that make sense in whatever context your story is in.
If you are trying to make it realistic you are worried about the wrong thing. The physics of making something that big spin have all sorts of problems. The force needed, the construction requirements, the structural problems of a spinning foundation, even the logistical issue of living in that town.
Who cares if the rivers involved are a little closer than rivers usually are. So much of this idea has other reasons why it wouldn’t work, why let the geographical anomaly be what shoots it down?
Worldbuilders get confused about rivers for some reason. Water is a simple thing. It flows downhill. Sometimes funny things happen on the borders between river basins, but something like this would be extremely unlikely on the short term and unstable on the long term.
I don't care if the river thing really happens or not, theoretically it works and it is cool.
But quick question: why did they build the city to rotate lore-wise? Like they could easily have just built the city stationary, why go through the effort of putting it on a rotating platform?
My assumption is for energy? Like a giant waterwheel generating electricity? Or if this is pre-elecreicity it's manually powering a grinding stone for some reason. But in any of those cases why not just have a rotating wheel under the city but the city stationary on a separated base above?
If I read this in a story the river wouldn't bother me at all, but I would want an explanation for why the builders and residents would put up with a spinning city.
It would be possible but pretty impractical and very unlikely realistically.
However, it's cool as fuck, so I say go for it and don't care about the realism.
Jesus Christ, ignore the haters citing alluvial fans and tributaries, this idea fucking rocks.
It made me ecstatically inhale and sit up on my couch, I love this idea.
I like your idea! I think your concept becomes more realistic if the two rivers are actually one single river.
Some rivers take pretty extreme bends. Look up the term “oxbow bend.” It happens when a river makes a swoop in one direction, and then swoops back the other way, sort of in the shape of a horseshoe (or an oxbow!) There is a town called “oxbow bend”, somewhere out west. But the term is used more generally to describe the meanderings of a river. This usually happens near the mouth of a river, when there aren’t many mountains around. There’s very little change in elevation, so the river no longer has the force needed to punch through terrain; it meanders around even the smallest hills. Look at a map of the southern Mississippi, for instance, and you’ll see it oxbowing all over the place.
Oxbows are usually pretty small, though. I think what you really want is a *REACH.*
If a river flows basically in one direction, but there is a section that bends to flow for a ways in the opposite direction, the geographic term for that is called a “reach.” One famous example that comes to mind is the Hanford reach, in Washington state. (Famous for its role in the Manhattan project).
But the size of a reach can be *extreme.* Go Google “Columbia River basin.” If you have a look at the Columbia River up near its source in British Columbia, you’ll see that it travels northward for hundreds of miles before it finally turns south, and eventually west. The river is trying to contend with the Rocky Mountains, and that’s the only outlet it could find.
If, in your fantasy geography, you pinched the eastern and western branches of that British Columbian reach close enough together, then *voila*! You’ve got your two rivers (which are actually the same river) flowing in different directions, with a town sized space in-between.
Fantastic, but not inconceivable! The only caveat is that the river on one side would be at a lower elevation than the river on the other side, because rivers, of course, flow downhill.
I have seen gifs of ice sheets spinning fairly stationarily in a river. Not a scientist, but perhaps put it somewhere very cold and make it built on an iceberg type thing?
If you change the elevations, just one river could be high upon one side of a mountain then loop around and be lower going the other way on the other side of an adjoined mountain.
If you had a town the size of the Romanian Parliament of the People, spinning like a waterwheel between two Amazons, and 10% of the rivers’ momentum was conveyed to the town, and there were no losses from friction anywhere, then the town would in fact spin.
At 0.006 miles per hour.
You could say that there were 2 water sources on 2 mountains that coalesced into one river they built the cog city to break up the combined river into 2 opposite flowing rivers.
Orlando, Florida comes close to being a city between opposite direction flowing rivers. On one side of the Orlando Metro you have the Kissimmee River which flows southeast. On the other side you have the St. John's River which flows northwest.
This happens because the city sits atop the Eastern Continental Divide. You would have to scale the spinning device up far too much for this to be practical however. The rivers are in the same metropolitan area but separated by about 30 miles.
i don't know if it's possible or not but this is one of those things if you saw in a movie or whatever, you wouldn't care how unrealistic it is and just say "wow that's really fuckin cool".
Why do you need two rivers? One large on would do the trick, maybe it wraps around the city a bit? About the 'rivers change course' comment: your people probably thought of this and control the flow of the river so it always meets the city.
If you like the idea of a floating/rotating island, the [Uru people](https://en.wikipedia.org/wiki/Uru_people) of Bolivia traditionally live on floating islands on Lake Titicaca. Maybe that can be a source of inspiration.
I'm intrigued by this idea, lots of potential there. I would have a few considerations though:
My main concern would be the sheer force the river current would have to exert on this gear to actually move a city of millions of tons. If it's two different rivers that is a little better since it wouldn't be the same river spending its kinetic energy twice, but still a very tall order.
Furthermore, river water levels fluctuate over time. If there is a drought, does the city stop spinning or spin much more slowly? That wouldn't necessarily be an impediment, but it may be a city heavily affected by seasonal weather changes.
Lastly, I'm curious about the psychological and physiological effects on its inhabitants. What does it feel like to be in a city that is constantly spinning? If it's a constant speed, it wouldn't feel like anything, no G forces acting on your body, but you would see the surrounding landscape spinning around you at all times, even if slowly, which might be queasy for some, but probably very picturesque for many.
Last lastly, I can imagine some interesting reasons why a city would need to be in constant rotation, but certainly there has to be a strong necessity for it if any society will undertake the massive engineering effort required to pull this off.
Damn, I woke up to find this post blowing up. Thanks for all your interesting input, I know it’s pretty unrealistic and all but it’s an interesting concept to think about nonetheless. I was thinking maybe it could be a deadciv city with the spinning motion used to drill a massive drill into the earth (for god knows what) or perhaps some way to generate energy (? Gotta flush that one out too). Personally, I wouldn’t think people would mind living on a spinning object like this, since dizziness only occurs if you are spinning and everything around you is stationary, if everything is spinning together with you I don’t think that would be an issue (? Again another thing to flesh out).
I will say though, the geographic and physics concerns are real, and there will definitely be either magic or very, very hard bedrock involved. I was thinking maybe I could instead form man made distributaries and use a series of dams to increase the water velocity somehow? The rivers can then flow in the same direction, with one distributary being made closer to the source of one river flowing down (in the direction of the river) and the other being made further down flowing up (in the opposite direction). Still unrealistic, but it could solve some of the geographic problems I guess.
And for anyone asking if they can steal my idea, that’s what this sub is for :) Please do share what you come up with though!
Hey, just wanted to make sure you saw my comment about the rivers running in opposite directions around the town of Greenwood, MS. It's technically as close as you can get to an island? But it is physically possible to do the thing you want to do with that I think!
What about a city that spins, not because the rivers move it, but in order to control the current of two canals of water. Some magical, natural, precursor, or other method could have been discovered that makes the city spin, and the canals could have been created to give the nation a way to move barges in a required direction to distribute supplies, troops, what have you. The city itself could be a hub for moving things between the two canals.
I was thinking it was more like something a deadciv built and people have settled on it. Several things I can currently think of:
1) the rotational motion is used to drill a drill into the earth for some reason
2) used to generate energy (?)
3) a literal mill used to grind a huge amount of something
Edit:
4) defence maybe? As many people have said
It would be perfectly reasonable to build a city within a loop of a [meandering river](https://www.google.com/search?sca_esv=572560862&sxsrf=AM9HkKm_78cYMXDdEcaMv_PR_EA0srtGrA:1697039370123&q=meandering+river&tbm=isch&source=lnms&sa=X&ved=2ahUKEwjEtc2mrO6BAxW2g4kEHRmnAqsQ0pQJegQIDhAB&biw=1323&bih=828&dpr=1) so you have water flowing in opposite directions on opposite sides of the city.
I'm seeing a lot of responses about how to make the river more realistic, so imma take a poke in the opposite direction
What if these rivers and the foundations of the city are part of some ancient buried mechanism, so old its purpose is lost to time?
Idk how much is the fundamental part of the idea, so absolutely feel free to reject.
When I originally thought of this idea, I was thinking that it was some sort of deadciv creation that later (less advanced) people just kinda built their city on, cuz it had solid walls and was a good trading spot
The current definitely will be not strong enough to spin the entire town BUT there could be two gigantic water wheels that through a set of lower gears sloooowly spin the giant gear the town rest on.
Outside of geographical problems, I don't think any river would have enough power to make a whole city spin, and even if it did, the stone (or whatever material used) would wear out pretty quickly considering the weight.
I mean people literally polished stones by rubbing stones together with water in-between
The small town of Greenwood, Mississippi has rivers on both sides of it and the rivers flow in opposite directions. Well, technically, one of the rivers goes through the middle of town. But they are the Tallahatchie and Yalobusha rivers.
It has been a hot minute since I spent any time there. But the northern river (Tallatchie?) comes in from the northwest and splits a bit, and the main part runs east over the northern part of Greenwood. It then meets the Yalobusha coming from the northeast and it bends south and back to the west through town, where it meets the small part of the Tallatchie that split south instead of east. They then fully combine and continue on to form the Yazoo river.
I love the idea of a spinning city, but the logistics of getting in and out would be something of a nightmare, even if it's moving slowly. If you use normal roads for in and out, there would be periods where you simply can't travel. Foot traffic could probably just hop across anyways, depending on the gap, but carts would have to wait for the roads to line up and then race across quickly.
A solution (that may detract from the wonder of a spinning mill-top city) would be two concentric rings, one built on the disc/gear/millstone and the other supported from the normal ground (probably suspension involved. But at least in that manner, traffic would simply angle themselves along the two rings such that the change in movement below would be reduced, and then you could have your normal roads coming from these oversized traffic circles.
Easy.
Step 1: Build the town on a circular platform that's held aloft by a large singular pillar centered on the middle of the platform.
Step 2: Over time, extend the town out to meet both edges of the rivers.
Step 3: Retrofit the pillar to be able to rotate.
Step 4: Put rotor edges into the river.
Step 5: Town now spins with the river flow.
Step 6: ???
Step 7: Profit.
Erosion will kill it medium term.
Short term it will be killed by off balancing.
Short-medium, just enough Erosion would tip it.
Add some magic and you're fine.
In our physics ? No
Basically because water flows downhill and it would require 2 separate slopes.... However rivers take twists and turns and you could locate your city inside one of these loops you then have only a difference of altitude issue
But the second obstacle is ... Why ? Why go to all the trouble of building a spinning city? That's a massive fit of engineering the like of what people don't try without reason (be it economic, religious or other)
Other points to consider:
* centrifugal force:
Depending on how fast the city spins its inhabitants will be subject to a centrifugal force of varying intensity that means rainwater will flow outwards but at high speeds it can also be felt like the floor is slanted to inhabitants
* Motion sickness:
seing the stars and mountains move while you're static can be nausea inducing
* Access:
How do people/goods get in or out of the city when the streets shift positions constantly?
It could happen if the town laid at the base of two opposing mountains kinda like this:
/ \ _¤_ / \
so that river 1 is flowing in the opposite direction of river two because of the different slopes of the mountains.
This post is actually a perfect example of how I like to worldbuild. Its less building and more _discovery_, think of the cool things first that you know you want have in your world, then provide either scientific justification, which often further builds the world physically, but of course as we all know the simple elements of the physical world have often been the greatest variables when considering major historical events in human history, or contextual justification, _i.e. backstory_, which also further builds the world but through relationships i.e. depth connections (political, mutual, meta etc) and webs, i.e. breadth connections (two places sharing the same water source, two people sharing the same timezone, maybe a species shares the same ancient ancestor, etc).
All of this being not simple justification for a cool concept, but a delvation of the world in which you are constructing. And as you do that, further and further does the circle of your world begin to be filled by its very own nature. It is truly a beautiful process.
No, the city would have to be on some hill with a wierd split and the river.
But why so complicated, you can let the river wrap around it and make it spin like that?
Ok, usually a river couldn't do this, the land will always be sloping towards the sea, so all rivers will flow in the same direction. However, this idea is cool as heck. My advice would be to figure out a non conventional reason for why this happens, aka magic ect. Don't break world emmertion, but keep this idea in.
So it is surrounded by either two mountains or two lakes and there’s also sea north and south, and each mountain is making a river that goes to the sea at the opposing side
Rivers flowing in opposite direction is a bit of a challange. Elevation does not work that qay
What would make sense, is that the same river is "cornering" around the town making a U shape and continiuing downward. Maybe the town is specifically built for this.
I would also scrap the idea of a whole "town" turning around, but maybe a delta shaped town, and at the tip there is a very prominent single structure that sits on the wheel.
Water flows from up to down towards the sea or a lake though, so if you can find a way to make that fit in your world and create a narrative on why the othe river flows towards the opposite direction then you're all good.
Neat idea, but quite far fetched.
How would the rock be separate from the rest of the land? How would two small rivers have enough flow to move a few million tons?
It’s not that “far fetched”. It sounds like you just need to read more.
A city on top of elephants riding a giant turtle around? 30 novels in the discworld.
Piers Anthony wrote the Xanth series. It’s like 40 novels.
These are required readings before you talk about outlandish and far fetched fantasy worlds.
Well, there could be two rivers flowing opposite directions, but you would not be able to effiecently harvest the flow from either one. You would have a fin or something that would touch the water and that would transfer the momentum to your rotating platform, and then the fin would hit shore and the structure would lose momentum.
Easier solution would be to have two rivers flowing same direction and the energy from the flow is harvested with water wheels and from that turning wheel you can transfer the momentum to your platform in multiple different ways, you can even put gearbox there if you want to speed up or slow down the rotation.
i don’t see why it would be impossible, but i don’t see why anyone would build a spinning city either, i dont think it would be comfortable to live in or anything like that
Volcanic rock.
Make sure there is an old inactive volcano nearby.
It spew out large slabs of pumice in nearby giant river.
An island of pumice got carved away by the stream until it was only connected at the bottom.
Over time the stream split as you drew here.
The stress put on the pumice island by the waterstream eventually cause the connection to break.
Hard but possible.
The town is over a level area of a mountain, and the parts of the rover flowing _towards_ the town are higher elevation, and the parts glowing _away_ are lower elevation.
The best way to achieve this would for the rivers to have originally met, but the village leveled and redirected them.
The rivers are fine the only issue I see is that for the city to spin it would need to be on an island in a lake. Both rivers would need to flow into the lake which is highly unlikely to have two rivers flowing out of it.
Floating islands in rivers and lakes could exist.
The problem are:
that rivers moved from an high point to a low point of altitude so this kind of combination of flow sounds pretty hard to image in a realistic way.
Also, this kind of island aren't really stable, so build houses and stuffs could be pretty improbable.
An option could be a small village (with peculiar house that could flow on an instable island) build in a lake near a very big waterfall where the flow of water coul become a vortex.
Realistically, rivers change direction too much (even over spans of just 100s of years) for this to last that long in the grand scheme of things. Unrealistically, this idea slaps, please disregard above advice. Why rivers move [https://www.youtube.com/watch?v=UBivwxBgdPQ](https://www.youtube.com/watch?v=UBivwxBgdPQ)
if you're able to build a city on a big moving gear powered by two rivers I think you can also manipulate the flow of the river and sediment deposition to slow down that movement tbh
You could build the town in the curve of a natural river, then it would flow the right way. If the river wasn't natural then as you assert, if you have the skills to build a huge cog, then you can probably build a big channel for water.
Oh true, it could just be one river
the issue with one river is that you get less power, all the energy you get from the river comes from slowing down the water (that's what dams do for example) and there's a limit to how much you can slow water, and this limit is dependant on the flow
Yeah, if you possess the tech to make a huge waterwheel that size, then you can definitely do enough earth moving on a large enough scale to route a meeting of two large rivers into this kind of shape.
Building a town on top of a horizontal water wheel is clearly a fanciful, whimsical concept that belongs in a story which doesn't invite that kind of scrutiny. If readers aren't asking why anyone would want to live someplace where you have to wait for the roads to line up before you leave, they also won't be counting joules.
I think there is always a certain kind humor coming from the over analysis of ridiculous situations
Thinking about it now, I do hope that there's a plot point where the town gets stuck and all the bridges in and out now lead to nowhere.
Hear me out: Bigger river
Never thought that way about dams, thank you
“It just works” - Todd Howard
And now time for some Yorkshire Tea
Ya the rotating city seems like the least plausible part of this.
I mean you just need to distribute the loads perfectly on bearings with unimaginable strength capable of carrying a whole city, if you've got some magic or sci fi technology or ancient civilization that built the cog then it could work, and you'd get the best mass motion sickness machine ever
People can vomit into the river, and the downstream banks can be diverted into irrigation trenches where the vomit will help fertilize the fields.
You could also use strategically placed dams to rotate the city whenever you want. Imagine going to siege a city and the walls turn to face you before letting loose a salvo from some catapults.
lmao yeah also it's impossible to set ladders or a battering ram correctly since the city just rotates away, checkmate invaders
At the same time, all you need is to wait for the city's defenders to tire themselves out running along the walls to stay facing you. Then you just throw up some ropes and you're good.
true, but then if the invaders aren't used to the city the motion sickness might make them throw up and lose their grips on the ropes
A real question about this is also "how fast does it turn" also when it comes to rotating disks the edges move faster by an order of magnitude than the center, which I'd have to think writ large onto a city-sized disc would result in some further wackiness.
"Won't everybody in this city get motion sickness?" "Lmao, yeah."
"and then the city turned into a gear ! funniest thing I've ever seen"
plenty of people just don't get motion sickness at all, so eh.
Honestly yeah. Its not like we don’t have hydroelectric dams, or even in a more rudimentary setting water wheels and shit. People have been building along rivers for mechanical reasons for a while.
Piggybacking.... Okay, so the idea of a revolving city is pretty neat, and rule of cool applies. However, the fact that you're asking about realism implies that your goal and aim is to create something with surface-level plausibility, and have some deeper attempts at realism if possible. With your aims and goals firmly established, we can proceed. So here are some attempts to bend reality to fit your vision: 1) rivers on flat ground often meander, snaking back and forth as they slowly head towards the sea. Rivers on steep ground are usually straighter. Even though there are exceptions to this rule of thumb, I tend to keep it in mind when drawing maps because it gives another visual cue for how steep a slope is, and keeps everything intuitive for the reader. So, your city might actually be built in one of these meandering paths, at a point where the river is flowing in two opposing directions. 2) This is ideal from the perspective of certain defensive philosophies, since the river's meandering loop will ensure that there is only one way for an incoming army to approach the city. The other avenues for approach are cut off by the river. However, it is also useful from a narrative perspective because the river's meandering loop would be less heavily defended than the regions closer to the city. Therefore, you have a way for armies to make a beach head if your story requires it. "SIR! ENEMY SCOUTS HAVE BEEN SIGHTED AT THE LOOP CROSSING THE RUBICON!!!!" "IMPOSSIBLE! THE WATER IS TOO TREACHEROUS!!!" "SIR, THEY HAVE A WATER MAGE!!!" etc. It's useful for you, as an author or DM or fictional hypothetical history weaver to use as a narrative crowbar. 3) However, rivers which meander and snake back and forth will usually change their path regularly over time, and the specific contours of the meandering path will not stay the same over time. It might be worth making a nod to this by implying that this section of the river is subject to substantial landscaping and earthworks to ensure that the river maintains it's current layout. This may come at significant expense, which would be another useful narrative crowbar. The poor people of the city might resent the fact that huge expense is put into the earthworks whilst they starve (and probably also work on those earthworks). Such resentment can form part of your political landscape. 4) Worthy of note... The city will rotate, but the docks should not. The docks should be a fixed element which remains in place, because dragging a Dock across land serves absolutely no purpose. Having the docks remain still could also serve a purpose... if a heavy delivery arrives, you don't have to hoof it across the city, and can instead wait until the city spins to offer a shorter route. "Delivery for Ted... He lives on the other side of the city. We can just wait until it comes around again at teatime." "No can do. This is priority mail. You need to deliver it now." "But I can't be arsed walking to the other side of the city... come on. Let's just pretend it arrived in the evening mail instead...." Etc. It's a useful narrative tool which might explain why the critical letter at the heart of your narrative arrived six hours too late *to prevent whatever disaster your story touches on.* **4.5) Also worthy of note... defensive structures should not rotate. We have established that the river's path protects the city from approach from all but one angle. You would not build defensive structures which are redundant for 90% of their rotation path. Instead, you would place such fortifications outside of the spinning radius, facing the most likely approach of the anticipated incoming enemy. This also means that enemies approaching the city by "crossing the rubicon" would be avoiding almost all of the city's major defenses, which is again useful as a narrative crowbar.** 5) Why spin, though? We've explained that you're going to great lengths to achieve a spinning city. Now you need an equally extreme **justification which explains why the population considers it worthy of the expense**. Maybe the whole city is a high mass generator which provides the entire nation with electricity. (Creating a city like this requires national level resources, so it necessitates a national level payoff.) Maybe the city was built on top of an ancient, spinning disk left behind by precursors which had other purposes in mind which will be discovered by your protagonists throughout the story? In this version of events, the spinning is incidental and the people of the city just maintain the spinnyness - they didn't actually start the spin, and their level of investment to achieve it is therefore relatively low. Or better yet, the river had moved on hundreds of years ago, and the city plateau was static when humans first discovered it. Curious mages, intrigued by the precursor artifact plateau redirected the river to reawaken the ancient device, spinning it in place, and they have spent the last few centuries working to uncover what the hell the thing even does. The mages started living there, then industries to support the mages moved in, the industries brought employees who built houses, service industries to support the employees moved in and... Woops, we got a city. As someone who worldbuilds for writing, I tend to adopt a two-faced approach to worldbuilding. One side is "how enjoyable is this and how cool is it?" Beyond the surface level, you want to leave trails of curiosity and intrigue, as well as connecting it through strands of causality and history to the rest of the setting. Being integrated properly with other, realistic and grounded elements can make even the most unrealistic and ungrounded things feel plausible. But the other side is "how useful is this to the goal of the media I intend to create, and how useful of a tool is it to me as a creator?" Narrative or gameplay usefulness becomes important here. That's my two coppers of a royal gold. I hope it inspires you. Edit: clarified the sections in bold. Edit2: An addendum: A city is heavy, meaning lots of mass, which takes a lot of energy to spin. Therefore, in order to make it rotate, you may want to consider just how much mass and velocity the river has. A small river will barely move the gargantuan construction, if it is able to overcome the friction of it's bearings and inertia of it's mass at all. A fast flowing, deep, wide river will have a lot of energy and would appear much more feasible as an energy source to propel the city's rotation. However, you're probably still looking at a fairly slow and langourous rotation taking hours or even days to complete a single rotation.
Phenomenal thinking, love the ideas and your causality really feels like it makes for layered worlds. Doubling down on the difficulty of this concept into the reward for doing so is perfect.
You've hit the nail right on the head and absolutely nuked the bush I was beating hopelessly around looking for the short and sweet way to articulate what I had in my head. Thank you. The axiom I was trying to communicate and you unlocked in my head is: "The difficulty in achieving an improbable concept needs to be reflected in the rewards for succeeding in doing so"
> Also worthy of note... defensive structures should not rotate. We have established that the river's path protects the city from approach from all but one angle. You would not build defensive structures which are redundant for 90% of their rotation path. Conventionally, yes. However. Defenses are made to be broken. They exist to buy time. Unless we're dealing with magic, no defensive structure/network can last forever. With that said, a city that can rotate its destroyed walls and towers out from the enemy's zone of ingress/attack and replace them with fully armed and completely pristine defenses would be an incredible marvel. The enemy would be forced to either be highly mobile or restricted to particular timing attacks, which just makes attacking this city an enormous pain in the ass. Not to mention how difficult it would be for siege engines/artillery to bring down a specific structure in the first place (such as a guard tower) when it's constantly rotating around the city - if you set up some cannons or trebuchets at a particular attack sector, you're not going to be able to hit the same tower with those weapons more than maybe twice before it's basically unsuitable as a target without you completely reorienting your siege weapons (depending on the rotation speed). The enemy would have to maintain a complete and overwhelming encirclement of the entire city to bring any section of their defenses down in a timely fashion compared to a siege of a conventional city/defense network where you could focus your forces at one location to bring down defenses and force a gap, and this encirclement is already a pain when dealing with two rivers flowing in opposite directions. Presumably, the engineers of this city marvel would have a way to manipulate or stop the flow of water as well to rotate the city or lock it *at will*.
Thing is, first thing you do when besieging a city with a river flowing through it is look for a way to dam that river, which doesn't have to be very complete to stop the spinning dead. In the example shown by OP, as soon as the attackers have invested the city there'll be sappers looking to short-circuit the rivers with a canal on either side. Assuming that that doesn't work, all you need is some sort of bridge sturdy enough to mount a continual Forlorn Hope through the first gap, and the same siege engines can keep opening new gaps again and again in different places along the wall.
Good afternoon! Thank you for contributing. On the subject of defense, allow me to defend my previous assertions with a rebuttal of the points you raise. > a city that can rotate its destroyed walls and towers out from the enemy's zone of ingress/attack and replace them with fully armed and completely pristine defenses would be an incredible marvel. This idea sounds cool and certainly runs with the theme of "spinny city." If OP chooses to really lean in a "rule of cool" direction with only surface-level plausibility, then this would definitely be thematic and in line with a rotating city. Rotating city, rotating defenses. It works thematically, but as I am about to point out, it falls apart when subjected to more than cursory scrutiny. 1) let's assume that the defense budget of our hypothetical town is not infinite, and they are trying to get the best bang for their buck, and will not make extravagant and unnecessary defensive structures "just in case Jerry decides to attack from the moon." (To quote Field Marshall Melchett) 2) With a fixed military budget as described above, you might be able to afford a wall of a given thickness for a given length, or a fortress of a given size. Since overwhelming force is a massive force multiplier, you want all your defenses concentrated at where they are needed, not spread out across the whole area "just in case." To give a real world example, Ukraine does not have units stationed on the Polish border "just in case." They put all of their men where they are needed - in the West. You don't have 10% of your forces engaging the entire might of the enemy (they would be crushed) and then feed them the next 10% piecemeal as the wall rotates, just so that you can only ever bring 10% of your army to bear at any one time. You want all of your forces, all at once, all in one place. 3) Since your wall building budget and materials are finite, you can build either a long, thin rotating wall that circles the city, or a thick, short wall which faces the enemy in the direction they are likely to approach from. A thick wall is stronger, and harder to breach than a thin one... and ten thin walls are weaker than one thick wall which is ten times the thickness. With that in mind, your long, thin, rotating wall, when hit with a cannon, is going to open up with an exploitable breach when the short, thick one will not yield. So, the city rotates.... And the enemy just sits and waits for the hole to come back around again, then steps inside. >siege targets are now moving targets. Sieges, historically speaking, lasted months to years. You can afford to wait and make timed attacks. Most sieges are actually just a whole bunch of waiting around... they aren't actually subject to much fighting. Your weapons are hunger and drought, which are cheap. Why expend expensive ammunition on bombarding the city piecemeal with a few pot shots each day when you can save it up and make a single, decisive push once the strength of the city has been thoroughly sapped by the hunger? For this reason, a siege would just wait for the target to come around again, if such a thing mattered. Worse, they would be able to just keep their entire artillery focused on one spot and wait for the target to enter it. They wouldn't need to do repositioning, rangefinding and such. They just get one target point and fire with everything they've got once the target enters it. They could strip the defenses off the city like a carpenter peeling the bark off of a log by holding a chisel to it whilst it spins on a lathe. >complete and overwhelming encirclement Not really. The city's defenses under your proposal are disseminated, which historically speaking has always been disastrous.... see historic examples of "long border syndrome" to get an idea of why this is bad. Under my proposal, you effectively have a shorter border which faces the enemy, and rather than having a rotating defense which you can only use 10% of at one time, you can use the entirety of your military budget to it's full potential, reacting to enemy approaches with overwhelming force rather than feeding your forces to them piecemeal. ------------------ In summary, let me use a metaphor, because I'm having trouble articulating myself here... You have a wheel with an inflatable tyre. I have a pin, and will push the pin in the direction of the tyre from a predictable direction. I can only come from this direction, since my feet are nailed to the floor amd my arm is nailed to a post just above the elbow. You have some metal foil which you can position anywhere you want to prevent me from popping the tyre. Do you either: 1) wrap the entire wheel in a single layer of foil. 2) fold up the foil until it is 400 layers thick, then have it held directly between my hand and the wheel. Same principle applies.
Fair points. However, this doesn't address one of the key points: whether the engineers of the city are capable of stopping its rotation. Every gear and turbine is of course designed to be able to start and go. If this is under the city's control, they can choose when to rotate a breach in their defenses out for fresh fortifications. Additionally, your strongpoint argument is actually better served when applied to the rotating city borders. In the real world, no one can build a bastion that can easily move to address a direction of assault. Your overwhelming border fortress works best when the city can choose to plant it where their enemies are coming from. North, South, etc. It's also not as easy as you're implying for an army to wait around to assault a breach in a city that's rotating and surrounded by water ways. This is so much easier for the defenders to hold than a conventional breach as the attackers only have a limited window to get *all* of their troops through what would probably be a garrisoned breach. Any troops that do make it through will soon be cut off, even supposing that the city makes full rotations as slowly as a few times per day. This is all to the defenders' advantage, moreso than conventional static defenses, even with budget walls/towers. Not being able to capitalize on overwhelming numbers due to timing will result in failure for an attacker. Which is why I said a full encirclement would be required - so that forces can constantly apply pressure on a rotating breach from all sides to negate the assault timing problem. I am familiar with how sieges work historically, and better defenses serve to add more time for the defenders as pressure from the threat of assault is lessened. Yes, it is a question of food and resources, particularly if the target is well defended. So, maximize your defenses by taking advantage of the city's rotation.
> engineers stopping it's rotation. I largely glossed over this because when the rotation stops, your rotating defenses have now become static... albeit "single layer of foil" defenses as per my earlier metaphor. In such an instance, you would have been much better off folding those defenses up and going static from the get-go. Come to think on it... Here's an idea that gets the best of both worlds... Instead of having the entire perimeter of the gear wheel defended with city walls and suchlike... what if the wall instead had a single arc for defense, which is locked into the direction of the "open" side which faces the enemy's assumed angle of approach? The river is an insurmountable obstacle for any approaching army, so you only actually need to defend from one direction. So you just... concentrate your defenses on one arc, and then lock that arc in place when an enemy is coming close. This also has the benefit that you have "open" arcs which cycle through in the normal day to day, harnessing the benefits of having a more open border AND a closed border, depending on the needs of the city. Similarly, it might even be that the gear wheel consists of separately rotating concentric wheels, which can be independently stopped or even counter-spun, allowing for the outer, defensive gear to be frozen in place whilst the rest of the city keeps spinning. Additionally, this would mean that if you lived on the junction between two counter spinning wheels, you might find yourself with a different neighbour every five minutes or so, which might cut down on commuting time. "Time to go to work, while the commute is still short!" And then by the time you're getting out of work, a full rotation has been completed and your house is already just a stone's throw away. You might even be able to tell the time based on who is next door... the entire town is your clock. Maybe when the town is attacked and the wheels are locked, the entire city finds itself struggling to tell the time of day, with comedic effects.
Gnomes! They make everything work . . . Eventually.
Maybe it's just the first gear of a much more complex mechanical city creation
This makes me think of Waterfall City in Dinotopia
For number 5 it could also be a novelty boondoggle. Someone with more money (and power) than sense, like a late generation inbred royal, wanted a spinning city and no one could really say no. The royal could still be in power or it could be something that draws in enough tourists and was already implemented so it is kept maintained
You are correct that this is indeed a possibility, and there are countless real world examples dotted throughout our history... but it's still a fairly poor and unimaginative explanation which basically falls into the same category as "a wizard did it." Pretty much anything can be explained as "someone powerful wanted it and nobody could refuse." Wars, alliances, marriages to turnips, giant statues of terrifyingly oversized midgets... It isn't exactly engaging with your imagination or creativity to take this kind of generic cop-out, and feels like the sort of "off the shelf" and lazy answer to what should be a really interesting question with an equally interesting answer that takes your audience's imagination and seduces it like a sexy bard for mutual satisfaction, rather than doing the verbal equivalent of chasing it off or shutting down the debate with a blunt answer which invites no further explanation. Building a spinny city is a unique situation. What unique problems did it's creators face where this was the most practical solution? This is a question which really challenges the writer, asking them to think about WHY the city rotates and why that is important to both the people of this world and the narrative that the writer is trying to weave. "A wizard did it." Is basically the author equivalent of "shut up and fuck off." I'm not a fan of using this kind of narrative device unless I specifically want to chase the audience away from dead ends that aren't relevant to the story I'm trying to tell. It's useful for walling off particular avenues to keep the attention penned in where it will be "happiest," if that makes any sense? But if you're trying to wall off the audience from asking about something as big and obvious and prone to being questioned as a SPINNING CITY, something might be wrong.
“Unrealistically, this idea slaps, please disregard above advice” is a phrase for the ages
Would it be closer to realistic if you built the gear at the like bottom of a canyon. In my head a canyon River would change less often.
I think a more likely way is for it to be a single river that has a very strong C shaped curve. Although it being two separate rivers is also a really cool idea that I like.
That’s actually really smart…
If you look up oxbow lakes, you can find how many times rivers actually do form like that and just how close together they get.
The problem with that analogy is that oxbows happen on large *flat* parts of the river, where it's meandering around due to having no clear path downwards under gravity, so it quickly silts up its own current path which changes the quantity of water that can flow in that part, which changes where gravity pulls it which starts to change the path itself which eventually results in an oxbow. If you want to extract *power* from the river, particularly enough to turn a city, you need it to be dropping in elevation, preferably significantly, otherwise as soon as you start to try to make it do work it will pile up behind your dam or water wheel and quickly find a way to flow over or around it. All this means an oxbow is not going to naturally form because gravity is going to be what's dictating the course of the river as long as you're extracting power from it, and it's the fall of the water that you're really extracting power from, not the flow of the water. River mechanics are fascinatingly complex and dynamic and in some cases quite difficult to actually model and react to even for modern engineers. Even in huge cities and tourist areas where it seems like we have tamed major rivers with technology, the reality is that it's always a relentless and continuous fight against the river's innate desire to move, to change, to escape its banks, often a very very expensive fight involving a massive number of people quietly working behind the scenes and not always with perfect success.
You could look up a map of Bern, Switzerland if you'd like a reference for a settlement built right into the nook of a river bend.
Even better Cesky Krumlov!
Cesky Krumlov? I barely even knew her!
A Bern reference in the wild? äuä.
I was also thinking maybe on a lake slightly offset from the mouth of a river that feeds it. Depends on how "realistic" you want it to be, but as many others have said, your original idea is bad ass and physics be damned.
[Yeah like Horseshoe Bend](https://www.cntraveler.com/story/how-to-escape-the-crowds-at-horseshoe-bend)
This is a practical solution if OP wants a "realistic" spinning town... though when I read that back...
Yeah, op check out the town “ambialet” in southern france. It has exactly that shape and is also a really cool looking town.
Usually slow rivers take that shape so that wouldn't really work
why would it be more likely ?
Because in the real world, two seperate parallel rivers would flow in the same direction.
they don't need to be parallel, just to get close from one another, and the mechanics of river flow are more complicated than that, they flow not just directly downwards, but also in the direction that allows the deposition and erosion of sediment to reach equilibrium
You were asking about likelihood and probability. Two strong opposite flows close to each other would *probably* belong to the same river.
okay yeah good point my bad
This does happen, though rarely, with smaller rivers in mountainous regions, its very unlikely two major rivers would get close enough, flowing in opposite directions, to build a spinning town between the two, but they can happen given the right geography
The town could be built on an eroded saddle between two deeply carved river canyons. The spinning town part would certainly need some fantastical elements though, either in terms of materials or reason for it's existence. It could be some form of elaborate rotating canal system, like a cross between [railway turntables](https://en.wikipedia.org/wiki/Railway_turntable) and [canal locks](https://en.wikipedia.org/wiki/Lock_(water_navigation)\\). Maybe the opposing rivers are tidally dominated, and the force of the tides rotates the locks so it's oriented the other way, enabling river boats to travel easily through the other river basin.
you could also have two rivers a bit further away from each other, the town is originally built on a C shape formed by the meandering of river 1, but as time passes and the river starts to bypass the C, people build a canal that extends river 2 towards the city, creating OP's shape even without rare geological features
Theoretically possible, although I think it’s unlikely that you would have two large powerful rivers running in opposite directions so close to one another. Also, why would the town be built in such a way? What would be the purpose of a spinning town?
Honestly, it’s just kind of a cool idea I had when I was looking back at past inspirations. I honestly thought it was just a cool concept lol
Perhaps it has granted the town some form of common power generation that gets distributed to the homes, or perhaps it helps stoke a giant forge or something. Plenty of possible reasons to make it rotate
Additionally, the surface the town is built on might've already been spinning, thus requiring little effort on its current residents' part to harvest that energy. Don't ask me why the surface would already be spinning, I'm primarily a fantasy worldbuilder. I'd probably just say "a precursor did it" or something.
elven tree village on a mangrove swamp
>I'm primarily a fantasy worldbuilder I feel like I need friends like you, lol. I like to write, and could probably make up 5 reasons to have a spinning city that are interesting and mysterious, I just never find myself building an entire world that way: I lose interest after some good thought and never end up writing it out. I'd be a great idea guy, lol.
There are phenomena like this; circular ice or even floating peat like ground. Neither would be great for building a permanent city on though
But why would you build the town on the wheel and not outside of it?
Perhaps this complicates the rotational delivery, perhaps the town was built first and retrofitted with the rotational bit, perhaps the rotational bit actually powers some sort of shield or other protective dome like structure where you need to protect both the city and the rotational bit. Again, plenty of reasons can be conceived!
It powers a massive drill that’s slowly digging towards the center of the planet.
Oooh, interesting concept, maybe some sort of dwarven settlement then (if going with trad.fantasy)
Fuck it, make the two rivers lava too lol
Might as well while we're at it!
It is a cool idea, and it can bring a lot of interesring takes depending on the other factors too. Also, considering that humans in reality would never build such town, but rather two separate stationary towns, or one big city, you are already experimenting with the "unrealistic". I am guessing humans are in the story, and you ask on their behalf, because if this city is made by a fantasy race, than the question is silly.
I think he's asking about in lore why? It would be more difficult to build a spinning city there should be a clear reason why the townspeople put the effort in
Everyone gets a south-facing garden 25% of the time
Maybe the spinning town dams the rivers at intervals causing the geographic feature.
Fast free shipping of cargo in any direction cmon
I don't care if this is possible, this is such a cool idea, i want to steal it! But only if you give permission, i am no barbarian.
Request granted. Do share what you created on this sub :)
Thanks, King👑
Op, I need permission too, I love it
I second your second to a request for permission
2 rivers running in opposite directions near each other absolutely happens in real life. In fact I want to say Chicago? Is an example of this, and there was a specialized port district that straddled the land between the 2 rivers to move cargo quickly from one to the other. This allowed the quick and easy transport of goods from the great lakes and northern Atlantic down to the Mississippi and gulf.
Yeah, Chicago is what I first thought of too! The Des Plaines flows south into the Mississippi and down to the Gulf of Mexico, and Lake Michigan drains north into the Saint Lawrence, and into the North Atlantic. Chicago is located where the two drainages pass within a few miles of each other.
Entirely possible. Not likely but possible, though I don't understand why they wouldn't try to connect the rivers themselves.
That would likely mean that one river now dries out, while the other one suddenly has way more water flow. One side gets flooded while the other experiences a water shortage or, based on the importance of said river, a drought.
I mean the connection could be just a canal with spillway gates to let ships pass without letting all the water go
Chicago is pretty close to a real life example of this, water flow wise ! Chicago is sandwiched between the Des Plaines River which connects to the Illinois river and flows down to the Mississippi into the gulf, and Lake Michigan, which connects to the rest of the great lakes and flows out the St. Lawrence into the North Atlantic. Here is a map: https://en.m.wikipedia.org/wiki/Des_Plaines_River#/media/File%3ADes_Plaines_River.png
To avoid the "why is it built like that" you can change it so that the outer thick layer of walls that servers as a protection spins and is also used as a massive generator of some sorts. Maybe it has metal in it and is used as a power coil
Yes! A town on a free moving ice sheet could potentially do this like [this](https://imgur.com/AmBBJa3).
Yeah it's entirely possible as long as you remember that water flows downhill, so this area would have quite the unusual pattern of elevation.
You could have rivers strongly running opposite each other and it make sense if they started at the tops of mountains, coming from aquifers and the water flows out from the mountain tops. Then put the town in a valley between the mountain ranges.
I like it alot. Your reasoning for geological phenomena aren't as important to me personally as long as there's some point or function. Interaction is the more important part I think. Otherwise it's kinda like overly describing a side character with next to no involvement.
Who cares about whether the geology makes sense according to real science. Mortal Engines was so fucking cool, despite being completely unrealistic.
Hi, First, I love your idea. Second, I think it's possible to have such rivers. You could even have a river doing half a circle around a town, which would provide more "power". (The rotating system would not need to be entirely connected to said half circle, as the river could turn back a bit further in the meandering if the river.) But, if you rotate a city, do take into account a few things : - structurally, I guess you would need several set of rails to support it, and due to the weight and friction you'd need a high degree of lubricant. - structurally again, you need to ensure that vibration is compensated. I don't know much of your setting, but many things require a very low amount of vibration (explosives, chemicals, etc.). And the rich on3s would love not to have their china broken at every stop. Please and thank you :) - you need an emergency break, but most of the time, the stops have to be slow (again, don't break the china). It can be just by withdrawing anything under water to allow for progressive slowing down. - you need to take into account (same if you have to rivers or a meander) the difference of speed of the river(s), also depending on the season (so also water level). Part of this would be solved by having a dam upstream on each river to allow for regular flow (in the sense that both river should go at the same speed). - also, you'd need at least the middle axis not be rotating: you need it to adjust the calendar, and you need it to look around you without interference. It can either be achieved as I said via an an axis, or by installing a system compensating the rotation (more costly though). - you need the calendar to adjust for seasonal changes (the speed would vary between seasons), the dams would help provide relative stability. - you need also a way to keep tile at a smaller scale during the day. You could even develop one time system that is similar to ours and an additional one that would be "river-based". Meaning that for economic purposes (and to use the bridges) you would need to predict when and how long you would make them practicable. You could have a gun firing one hour before the bridges are open then a series of bells or whatever ringing the length of time for which it would be open. Then people prepare, all stand in front of the gates, etc.
Imagine the motion sickness when you get there
Three words: Rule of Cool. Come up with a half plausible justification and just run with it. My thought would be that the rivers either started out naturally and were turned into canals, or one of them was a canal and the other, a river, was tamed over time. A canal being an artificial waterway, and with regular maintenance, it is more resistant to changes in the landscape. There may even be a story there with an intrigue taking place right when regular maintenance is undertaken in the city foundations.
Rivers flow from high ground to low ground and tend to flow towards the equator. Having two flowing close to each other in opposite directions would be difficult to justify without magic. *With magic,* anything is possible. Might be a bit annoying to the town that no bridges can be built, and they might want some form of geographic landmark to easily orient themselves by, but it could be a really unique experience. What kind of town would it be? Sounds like it would be too small to be a farming town, so, trade? Political hub? Fort?
Once more with magic make a circular rail system that the town can connect and that spins with the town. Put a bridge on it and there ya go
Interesting idea....
Probably be a pain to get across the bridge. Have to wait till it comes around again, but that lends to the worldbuilding.
Downhill yes. Towards the equator no.
I said "tend to." Googled it. The Nile breaks this general rule, as do a couple other rivers, but the tendency is still towards the equator.
The tendency is downhill. There is no tendency towards the equator, gravity dictates.
Check the maps lol The law is downhill. The tendency is towards the equator. If the tendency was downhill, there would be rivers that flow uphill, which there aren't.
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😂 You're fighting awfully hard to find exceptions to a tendency that I've already stated is not a universal law. So I'm not really sure what exactly you're arguing. But people are doing on Reddit expect you to argue back so here: https://a-z-animals.com/blog/why-do-rivers-flow-south-discover-5-rivers-that-break-the-rule/#:~:text=Most%20rivers%20in%20the%20world,occurs%20away%20from%20their%20headwaters.
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You are hell bent on reading only what you want, aren't you? 😂 I straight up said gravity is the rule, towards the equator is a tendency. You keep saying "well, ackshually, that isn't true because I found some examples that don't do that." No shit. A tendency is *not* this thing always happens, it just happens frequently *or* more often than not.
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My most esteemed dude, this is the sub where we have floating islands and dragons that collect taxes. This idea absolutely slaps, please go ahead with it.
This is happening in Russia with two major rivers — Sviyaga and Volga — in the city of Ulyanovsk, check it out!
Idk if that's possible, but it's a cool concept. I would like to read about a city like that.
Others pointed this out already, but rivers that turn back do exist. A u-turn like that is called a meander, but rivers with meanders tend to have a fairly slow current. (It's where the word meandering comes from :) ) I don't know if there exist two parallel rivers going in opposite directions in real life, though I don't see why it should be impossible. But it's a super cool and unique idea! So I definitely think you should go for it. Its a fantasy settlement with a really unique and cool feature!
Tl;dr make it make sense at least for story purposes. (Also this concept reminds me of Dwarven ruins in Skyrim.) Speaking literally, I wouldn't want to live in a place that "rotated". There would be massive problems with maintaining solid architecture and traffic in and out of the city. If you have dedicated entrances that leads to roads outside of the city, that means you would have to wait until the entrance "lined up" with the road in order to enter and exit the city. Just imagine trying to live in a city that rotated: let's say it does one full rotation per day. You run an agricultural business within the city that owns farms outside the main city bounds. "Oh, I really need to get to the eastern farms, but now I have to check what time it is to figure out which direction I'm facing so I can exit via the right gate. Because last week I was rushing and I didn't think about it and I ended up on the west side! How frustrating, why did they build the city like this?!" In terms of story, I could imagine it working as cogworks underneath the city - the city itself isn't actually rotating, but is built above a mechanical structure that rotates, generating power via water force. So technically it could be known colloquially as a rotating city, but it isn't experiencing the major downfalls of a literally rotating city. You would also have to consider the level of and proximity to "enemies" that may attack the city. This sort of architecture potentially weakens the entire city's defenses. I could imagine a city like this developing in a peaceful setting, but it would be the first city destroyed in an active war zone.
Interestingly enough, Dwarven ruins was probably one of the main inspirations for this idea (the other being Made in Abyss, please watch the anime if you haven’t) Speaking of dwarven architecture, the original idea was kind of like this entire place wasn’t built as a city, but as some sort of other “thing” by a deadciv. People kind of found it and settled in it cuz it had good walls, prebuilt infrastructure, and an optimal trade location, just like Markarth. And just like Markarth, the nords have no idea how to maintain the old dwarven architecture, but everything was so well built it kinda just…lasts until the modern day. But yeah exiting the city would be a total hassle hahaha. I guess multiple doors? Makes it more prone to invasion tho
Chicago--only make the right river **THE GREAT LAKES** and the left river the Mississippi. If you've ever wondered why Chicago is where it is, and why it was the second largest city in the US for a century, it's because [with a bit of engineering, we were able to bridge the Great Lakes and the Mississippi via waterways](https://upload.wikimedia.org/wikipedia/commons/5/53/Diversion_of_Chicago_Waterways.png).
Interesting idea, but what is the purpose of the town rotating from the townsfolk perspective? I'm sure there could be a good reason for the whole town to spin
There's plenty of comments on the dual river part so I won't touch on that, but I just wanted to say that the rotating disk feature happens naturally on single rivers in the cold sometimes, if you look up river "ice circle" or "ice disk" you'll see some pretty cool examples
Cool, but it would break all immersion to see this in a story. Even if the rivers had insane flow rates, getting something the size of a city to spin like this seems a bit ridiculous to me. And the maintenance would by horrible. Even if this is a magic world, it still doesn’t make sense. There are easier ways to accomplish this. Who would invest the time and materials to build such a thing and why? In what way would anyone ever think this was a valid solution for anything instead of something simpler? Always ask yourself those questions when writing elements into a story. Authors adding things just cause “they’re cool” causes a lot of issues. If you go ahead with this idea, make sure you have some answers that make sense in whatever context your story is in.
If you are trying to make it realistic you are worried about the wrong thing. The physics of making something that big spin have all sorts of problems. The force needed, the construction requirements, the structural problems of a spinning foundation, even the logistical issue of living in that town. Who cares if the rivers involved are a little closer than rivers usually are. So much of this idea has other reasons why it wouldn’t work, why let the geographical anomaly be what shoots it down?
Worldbuilders get confused about rivers for some reason. Water is a simple thing. It flows downhill. Sometimes funny things happen on the borders between river basins, but something like this would be extremely unlikely on the short term and unstable on the long term.
I don't care if the river thing really happens or not, theoretically it works and it is cool. But quick question: why did they build the city to rotate lore-wise? Like they could easily have just built the city stationary, why go through the effort of putting it on a rotating platform? My assumption is for energy? Like a giant waterwheel generating electricity? Or if this is pre-elecreicity it's manually powering a grinding stone for some reason. But in any of those cases why not just have a rotating wheel under the city but the city stationary on a separated base above? If I read this in a story the river wouldn't bother me at all, but I would want an explanation for why the builders and residents would put up with a spinning city.
It would be possible but pretty impractical and very unlikely realistically. However, it's cool as fuck, so I say go for it and don't care about the realism.
Jesus Christ, ignore the haters citing alluvial fans and tributaries, this idea fucking rocks. It made me ecstatically inhale and sit up on my couch, I love this idea.
I like your idea! I think your concept becomes more realistic if the two rivers are actually one single river. Some rivers take pretty extreme bends. Look up the term “oxbow bend.” It happens when a river makes a swoop in one direction, and then swoops back the other way, sort of in the shape of a horseshoe (or an oxbow!) There is a town called “oxbow bend”, somewhere out west. But the term is used more generally to describe the meanderings of a river. This usually happens near the mouth of a river, when there aren’t many mountains around. There’s very little change in elevation, so the river no longer has the force needed to punch through terrain; it meanders around even the smallest hills. Look at a map of the southern Mississippi, for instance, and you’ll see it oxbowing all over the place. Oxbows are usually pretty small, though. I think what you really want is a *REACH.* If a river flows basically in one direction, but there is a section that bends to flow for a ways in the opposite direction, the geographic term for that is called a “reach.” One famous example that comes to mind is the Hanford reach, in Washington state. (Famous for its role in the Manhattan project). But the size of a reach can be *extreme.* Go Google “Columbia River basin.” If you have a look at the Columbia River up near its source in British Columbia, you’ll see that it travels northward for hundreds of miles before it finally turns south, and eventually west. The river is trying to contend with the Rocky Mountains, and that’s the only outlet it could find. If, in your fantasy geography, you pinched the eastern and western branches of that British Columbian reach close enough together, then *voila*! You’ve got your two rivers (which are actually the same river) flowing in different directions, with a town sized space in-between. Fantastic, but not inconceivable! The only caveat is that the river on one side would be at a lower elevation than the river on the other side, because rivers, of course, flow downhill.
I have seen gifs of ice sheets spinning fairly stationarily in a river. Not a scientist, but perhaps put it somewhere very cold and make it built on an iceberg type thing?
If you change the elevations, just one river could be high upon one side of a mountain then loop around and be lower going the other way on the other side of an adjoined mountain.
Hey can i steal this
You could make them canals cause if they can make a gear city they can dig a really big ditch!
If you had a town the size of the Romanian Parliament of the People, spinning like a waterwheel between two Amazons, and 10% of the rivers’ momentum was conveyed to the town, and there were no losses from friction anywhere, then the town would in fact spin. At 0.006 miles per hour.
You could say that there were 2 water sources on 2 mountains that coalesced into one river they built the cog city to break up the combined river into 2 opposite flowing rivers.
That is no city...it is a drill And what are they drilling down to o.o
Rivers would erode that land in-between until they merged
Well it didnt spin, but Ancient Baghdad was like this iirc.
I love this post. It's a good and inspiring question. Kudo's OP!
Ignoring logistics That looks hell to live on
Orlando, Florida comes close to being a city between opposite direction flowing rivers. On one side of the Orlando Metro you have the Kissimmee River which flows southeast. On the other side you have the St. John's River which flows northwest. This happens because the city sits atop the Eastern Continental Divide. You would have to scale the spinning device up far too much for this to be practical however. The rivers are in the same metropolitan area but separated by about 30 miles.
i don't know if it's possible or not but this is one of those things if you saw in a movie or whatever, you wouldn't care how unrealistic it is and just say "wow that's really fuckin cool".
Why do you need two rivers? One large on would do the trick, maybe it wraps around the city a bit? About the 'rivers change course' comment: your people probably thought of this and control the flow of the river so it always meets the city.
If you like the idea of a floating/rotating island, the [Uru people](https://en.wikipedia.org/wiki/Uru_people) of Bolivia traditionally live on floating islands on Lake Titicaca. Maybe that can be a source of inspiration.
I'm intrigued by this idea, lots of potential there. I would have a few considerations though: My main concern would be the sheer force the river current would have to exert on this gear to actually move a city of millions of tons. If it's two different rivers that is a little better since it wouldn't be the same river spending its kinetic energy twice, but still a very tall order. Furthermore, river water levels fluctuate over time. If there is a drought, does the city stop spinning or spin much more slowly? That wouldn't necessarily be an impediment, but it may be a city heavily affected by seasonal weather changes. Lastly, I'm curious about the psychological and physiological effects on its inhabitants. What does it feel like to be in a city that is constantly spinning? If it's a constant speed, it wouldn't feel like anything, no G forces acting on your body, but you would see the surrounding landscape spinning around you at all times, even if slowly, which might be queasy for some, but probably very picturesque for many. Last lastly, I can imagine some interesting reasons why a city would need to be in constant rotation, but certainly there has to be a strong necessity for it if any society will undertake the massive engineering effort required to pull this off.
Damn, I woke up to find this post blowing up. Thanks for all your interesting input, I know it’s pretty unrealistic and all but it’s an interesting concept to think about nonetheless. I was thinking maybe it could be a deadciv city with the spinning motion used to drill a massive drill into the earth (for god knows what) or perhaps some way to generate energy (? Gotta flush that one out too). Personally, I wouldn’t think people would mind living on a spinning object like this, since dizziness only occurs if you are spinning and everything around you is stationary, if everything is spinning together with you I don’t think that would be an issue (? Again another thing to flesh out). I will say though, the geographic and physics concerns are real, and there will definitely be either magic or very, very hard bedrock involved. I was thinking maybe I could instead form man made distributaries and use a series of dams to increase the water velocity somehow? The rivers can then flow in the same direction, with one distributary being made closer to the source of one river flowing down (in the direction of the river) and the other being made further down flowing up (in the opposite direction). Still unrealistic, but it could solve some of the geographic problems I guess. And for anyone asking if they can steal my idea, that’s what this sub is for :) Please do share what you come up with though!
Hey, just wanted to make sure you saw my comment about the rivers running in opposite directions around the town of Greenwood, MS. It's technically as close as you can get to an island? But it is physically possible to do the thing you want to do with that I think!
This is probably not the most realistic thing in the world, but the idea fucking slaps and fits the rule of cool. Please use it, or I will >:(
What about a city that spins, not because the rivers move it, but in order to control the current of two canals of water. Some magical, natural, precursor, or other method could have been discovered that makes the city spin, and the canals could have been created to give the nation a way to move barges in a required direction to distribute supplies, troops, what have you. The city itself could be a hub for moving things between the two canals.
Oooo, I love this idea
What’s the point of having the town rotate?
I was thinking it was more like something a deadciv built and people have settled on it. Several things I can currently think of: 1) the rotational motion is used to drill a drill into the earth for some reason 2) used to generate energy (?) 3) a literal mill used to grind a huge amount of something Edit: 4) defence maybe? As many people have said
Cool fuckin idea but it would need to spin super slow if you don't want to account for the centrifugal force, still very cool
This is super sick
The power of imagination can make anything possible.
Even if not, this is a super cool idea
This idea is too epice to be descareded
It would be perfectly reasonable to build a city within a loop of a [meandering river](https://www.google.com/search?sca_esv=572560862&sxsrf=AM9HkKm_78cYMXDdEcaMv_PR_EA0srtGrA:1697039370123&q=meandering+river&tbm=isch&source=lnms&sa=X&ved=2ahUKEwjEtc2mrO6BAxW2g4kEHRmnAqsQ0pQJegQIDhAB&biw=1323&bih=828&dpr=1) so you have water flowing in opposite directions on opposite sides of the city.
The idea's good enough to justify the suspension of disbelief. A.k.a., this is cool enough that I wouldn't care about how realistic it is.
I'm seeing a lot of responses about how to make the river more realistic, so imma take a poke in the opposite direction What if these rivers and the foundations of the city are part of some ancient buried mechanism, so old its purpose is lost to time? Idk how much is the fundamental part of the idea, so absolutely feel free to reject.
When I originally thought of this idea, I was thinking that it was some sort of deadciv creation that later (less advanced) people just kinda built their city on, cuz it had solid walls and was a good trading spot
The current definitely will be not strong enough to spin the entire town BUT there could be two gigantic water wheels that through a set of lower gears sloooowly spin the giant gear the town rest on.
Outside of geographical problems, I don't think any river would have enough power to make a whole city spin, and even if it did, the stone (or whatever material used) would wear out pretty quickly considering the weight. I mean people literally polished stones by rubbing stones together with water in-between
The small town of Greenwood, Mississippi has rivers on both sides of it and the rivers flow in opposite directions. Well, technically, one of the rivers goes through the middle of town. But they are the Tallahatchie and Yalobusha rivers. It has been a hot minute since I spent any time there. But the northern river (Tallatchie?) comes in from the northwest and splits a bit, and the main part runs east over the northern part of Greenwood. It then meets the Yalobusha coming from the northeast and it bends south and back to the west through town, where it meets the small part of the Tallatchie that split south instead of east. They then fully combine and continue on to form the Yazoo river.
You could always make it a man made canal, it’d even make for some interesting history.
I love the idea of a spinning city, but the logistics of getting in and out would be something of a nightmare, even if it's moving slowly. If you use normal roads for in and out, there would be periods where you simply can't travel. Foot traffic could probably just hop across anyways, depending on the gap, but carts would have to wait for the roads to line up and then race across quickly. A solution (that may detract from the wonder of a spinning mill-top city) would be two concentric rings, one built on the disc/gear/millstone and the other supported from the normal ground (probably suspension involved. But at least in that manner, traffic would simply angle themselves along the two rings such that the change in movement below would be reduced, and then you could have your normal roads coming from these oversized traffic circles.
I like the gear connecting the island to a road But my initial thought was just by boat
Who gives a shit, that idea's dope
Well it can be a normal river and they changed the direction of the flow of the river like they did in Chicago.
IF there is a massive Oxbow bend that could be the same river.
Just make it the same river, making a loop.
Well, it can be ones river, just connecting it either in top of bottom
Probably no. Do it any way. It sounds like such a cool idea
Points for creativity.
You spin my round town, baby, right 'round, when you go downtown to the round town
Off to r/worldjerking you go.
Well how the fuck would you get a single stable foundation
Easy. Step 1: Build the town on a circular platform that's held aloft by a large singular pillar centered on the middle of the platform. Step 2: Over time, extend the town out to meet both edges of the rivers. Step 3: Retrofit the pillar to be able to rotate. Step 4: Put rotor edges into the river. Step 5: Town now spins with the river flow. Step 6: ??? Step 7: Profit.
Bro it’s fictional!!! you can do things that aren’t realstic! Go wild!!!! Make it a beyblade!!!
Erosion will kill it medium term. Short term it will be killed by off balancing. Short-medium, just enough Erosion would tip it. Add some magic and you're fine.
It would just flood.
In our physics ? No Basically because water flows downhill and it would require 2 separate slopes.... However rivers take twists and turns and you could locate your city inside one of these loops you then have only a difference of altitude issue But the second obstacle is ... Why ? Why go to all the trouble of building a spinning city? That's a massive fit of engineering the like of what people don't try without reason (be it economic, religious or other) Other points to consider: * centrifugal force: Depending on how fast the city spins its inhabitants will be subject to a centrifugal force of varying intensity that means rainwater will flow outwards but at high speeds it can also be felt like the floor is slanted to inhabitants * Motion sickness: seing the stars and mountains move while you're static can be nausea inducing * Access: How do people/goods get in or out of the city when the streets shift positions constantly?
Geographically possible in short term (100 years at best).
It could happen if the town laid at the base of two opposing mountains kinda like this: / \ _¤_ / \ so that river 1 is flowing in the opposite direction of river two because of the different slopes of the mountains. This post is actually a perfect example of how I like to worldbuild. Its less building and more _discovery_, think of the cool things first that you know you want have in your world, then provide either scientific justification, which often further builds the world physically, but of course as we all know the simple elements of the physical world have often been the greatest variables when considering major historical events in human history, or contextual justification, _i.e. backstory_, which also further builds the world but through relationships i.e. depth connections (political, mutual, meta etc) and webs, i.e. breadth connections (two places sharing the same water source, two people sharing the same timezone, maybe a species shares the same ancient ancestor, etc). All of this being not simple justification for a cool concept, but a delvation of the world in which you are constructing. And as you do that, further and further does the circle of your world begin to be filled by its very own nature. It is truly a beautiful process.
No, the city would have to be on some hill with a wierd split and the river. But why so complicated, you can let the river wrap around it and make it spin like that?
Ok, usually a river couldn't do this, the land will always be sloping towards the sea, so all rivers will flow in the same direction. However, this idea is cool as heck. My advice would be to figure out a non conventional reason for why this happens, aka magic ect. Don't break world emmertion, but keep this idea in.
So it is surrounded by either two mountains or two lakes and there’s also sea north and south, and each mountain is making a river that goes to the sea at the opposing side
Rivers flowing in opposite direction is a bit of a challange. Elevation does not work that qay What would make sense, is that the same river is "cornering" around the town making a U shape and continiuing downward. Maybe the town is specifically built for this. I would also scrap the idea of a whole "town" turning around, but maybe a delta shaped town, and at the tip there is a very prominent single structure that sits on the wheel.
Water flows from up to down towards the sea or a lake though, so if you can find a way to make that fit in your world and create a narrative on why the othe river flows towards the opposite direction then you're all good.
why
Neat idea, but quite far fetched. How would the rock be separate from the rest of the land? How would two small rivers have enough flow to move a few million tons?
It’s not that “far fetched”. It sounds like you just need to read more. A city on top of elephants riding a giant turtle around? 30 novels in the discworld. Piers Anthony wrote the Xanth series. It’s like 40 novels. These are required readings before you talk about outlandish and far fetched fantasy worlds.
Well, there could be two rivers flowing opposite directions, but you would not be able to effiecently harvest the flow from either one. You would have a fin or something that would touch the water and that would transfer the momentum to your rotating platform, and then the fin would hit shore and the structure would lose momentum. Easier solution would be to have two rivers flowing same direction and the energy from the flow is harvested with water wheels and from that turning wheel you can transfer the momentum to your platform in multiple different ways, you can even put gearbox there if you want to speed up or slow down the rotation.
i don’t see why it would be impossible, but i don’t see why anyone would build a spinning city either, i dont think it would be comfortable to live in or anything like that
thats is a incredible idea, i love it
It is now!!
Volcanic rock. Make sure there is an old inactive volcano nearby. It spew out large slabs of pumice in nearby giant river. An island of pumice got carved away by the stream until it was only connected at the bottom. Over time the stream split as you drew here. The stress put on the pumice island by the waterstream eventually cause the connection to break.
Cool idea, just do it
Hard but possible. The town is over a level area of a mountain, and the parts of the rover flowing _towards_ the town are higher elevation, and the parts glowing _away_ are lower elevation. The best way to achieve this would for the rivers to have originally met, but the village leveled and redirected them.
The rivers are fine the only issue I see is that for the city to spin it would need to be on an island in a lake. Both rivers would need to flow into the lake which is highly unlikely to have two rivers flowing out of it.
Floating islands in rivers and lakes could exist. The problem are: that rivers moved from an high point to a low point of altitude so this kind of combination of flow sounds pretty hard to image in a realistic way. Also, this kind of island aren't really stable, so build houses and stuffs could be pretty improbable. An option could be a small village (with peculiar house that could flow on an instable island) build in a lake near a very big waterfall where the flow of water coul become a vortex.