For my world I would need a really large swamp (or similar kind of wetland). It should be about 200km in diameter, which should be quite possible given a large enough flat terrain and enough rain.

The problem is that this environment needs to be completely isolated from the mainland: my small humanoids (around 70cm high), that have a technological level similar to that of natives of the Amazon basin, shouln't be able to reach the mainland or, if possible, shouldn't even know of it's existence.

Unfortunately, putting the swamp in the middle of the ocean like an island isn't an option, as the kind of plants able to grow in such saline environments are not suited to the environment I want to create.

This would lead to the need for a really large lake, which raises two questions:

  1. Is it even possible for a swamp to exist in the middle of such a large lake?
  2. I know It's possible for large lakes to have currents, winds and tidal movements, and even seasonal currents, like the Great Lakes; but could there be any conditions under which these currents and winds are so strong as to make it impossible for my civilization to cross this barrier? This could also help justify their knowledge of the existence of the mainland without any settlers there, and could lead to quite a bit of mythology I might get interested in.
  • $\begingroup$ I feel obliged to ask, if the lake is so difficult to navigate, how did anyone end up living on the island in the first place? $\endgroup$
    – Cadence
    Mar 7, 2019 at 21:35
  • $\begingroup$ @Cadence they evolved from flying creatures finding a place without predators and with ample sources of food, so they abandoned flying and settled there. $\endgroup$ Mar 7, 2019 at 21:37

2 Answers 2


To have a swamp, you have to have 3 things:

  1. A flat area to collect water that slowly drains out (you want a swamp, not a lake).
  2. Somewhere for water to collect that feeds water into the flat area (mountains) around a large portion of the flat area so you don't have just one source cutting a river channel through it.
  3. Rain. Lots and lots of rain.

If you have impassible mountains around a good chunk of the swamp and ocean on the free edge(s), it is unlikely that you will have a lot of traffic to the area.

It seems to me that you are looking for something very like the Amazon Basin you mentioned. You could, essentially, make South America an island but you said that you don't want an island. If you make the mountains taller, you can cut the area off from the rest of the mainland. the trick is to have them tall enough that even the passes are well above the tree line. That way the only way to the swamp is to sail there.

In this scenario, the swamp could well be seen as "past the edge of the world."

  • $\begingroup$ This might very well be the thing I was searching for, the idea of having mountains isolating some kind of "water-heavy valley" hand't even grazed my mind. As of right now, this is probably better than any solution I may have came up with. $\endgroup$ Mar 7, 2019 at 21:55
  • $\begingroup$ @NicholasMazzer, The other good thing is that the mountains will draw almost all of the water from the air. So, the far side of the mountains will likely be a desert unless there is a large source of water nearby. that makes it even harder to get to the swamp. $\endgroup$
    – ShadoCat
    Mar 7, 2019 at 22:03

Put it on a mountaintop.

https://www.researchgate.net/figure/Maringma-tepui-Authors-tent-on-the-very-top-of-the-mountain-looking-SWW-Mount-Roraima_fig4_259759794 swamp

Depicted: Maringma-tepui

Maringma-tepui has a maximum elevation of around 2,147 m (7,044 ft)1 or 2,134 m (7,001 ft).[3] The summit plateau has an area of roughly 170 hectares (420 acres) and is highly uneven, allowing water to collect in many deep, swamp-like pools.[5] It is predominantly covered in low-growing "tepui meadow" vegetation, quaking peat bog, and some dwarf forests of Bonnetia roraimae, with few areas of exposed rock.1[5]

Here is Maringma-tepui from a distance.


When I was in Kauai, I went up onto a mountaintop and was surprised to find a swamp with boardwalks up there. The coolest thing were all the tiny sundew flower - these mountaintop swamps are nitrogen poor but rich in insects that get blown up there, and so good habitats for carnivorous plants. What you need is a depression up there that can collect water and a substrate that prevents it from draining away.

Tepuis have been used as isolated habitats in lots of fictions - their steep walls limit access and egress and all sorts of weird stuff might be hiding on top. The top of a steep sided tepui would be perfect for your swamp people.

  • 2
    $\begingroup$ This is also a very good idea, and it would help with finding the reason for the near-total absence of predators in the area. Also, the presence of carnivorous plants is a real added bonus, as they are a central part of the mythos of my civilization. But I do find difficult for such an environment able to support a population of 60k+ individuals living on top of a mountain, even if the mountain top is really large, and would make their mostly fish based diet more difficult to obtain as I doubt this closed of an environment could support large fish population. $\endgroup$ Mar 7, 2019 at 22:13
  • $\begingroup$ Having a 200 km wide mountain plateau, which is both enclosed and wet? Hmm, I'm skeptical. $\endgroup$
    – Alexander
    Mar 7, 2019 at 22:39
  • 2
    $\begingroup$ Auyán-tepui has a summit area of 667 square kilometers. That's larger than Barbados (pop 278,000, area 439 km2), Grenada (pop 107,000, 310 km2), and is about the same size as Cozumel (pop 100,000). Getting fish up there is admittedly a problem, but not an insurmountable one. Many tepuis have cave systems that go down, and you can always handwave that caves descend from the summit to cave systems below that are connected to larger waterways via underground channels that fish can use. $\endgroup$ Mar 7, 2019 at 22:48

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