Real life must’ve seemed like this for a really long while, until it all of a sudden didn’t anymore.

When they look up, it looks like this:

This would make an excellent tv series (animated or otherwise). Any time things start to get stale, introduce a new group of people. Some aggressive, some peaceful, some pirates aiming to get rich. Maybe throw in a big “all go the same way” cultural movement just to be silly. It would do amazingly for the episodic format or a continuing story format, or even a blend of the two. Maybe a different group of travelers every season, maybe different groups that are shown in turns and eventually meet up or something.

But I don’t think I’d likely want to read it as a book series.. it feels like the sort of concept that would very quickly escape most authors and just sort of meander on forever.. maybe someone like pratchet who does complicated intertwined world building anyway, but it would require a very specific sort of author to do well, where a show series of that sort would necessitate a team of people working on it to sort of keep it in check.

HxH dark continent be like

A bit like the short story "Tower of Babylon", by Ted Chiang.

Ultraviolet Grasslands would be good for this

Presumably at some point they would figure out that their skybox is fixed in a way that either doesn't actually follow any rules of basic trignonometry, and thus is a simulation/projection, or, they'd find that it does follow the rules of trig, and that would prove that their world has 0 curvature.

If Eratosthenes had done what he'd done, in that world, he would have pretty definitively concluded that the world is indeed provably flat, and is potentially an infinite plane, around ~ 220 BCE.

Also: How do 'days' work, on an infinite flat plane?

This is actual flat earther levels of nonsense if you think about it for like, 15 seconds.

Here's a better world building idea:

Build your alt history or fantasy or post apoc world (why not all three?) on a world that is totally covered in a very thick atmosphere, or has some property by which there is essentially always 100% cloud cover, basically everywhere.

It can be flat, or not.

Astronomy and thus our whole tech tree path for like half of science is now essentially impossible.

It would follow a totally different pattern of development of thought and ideas, in many ways.

Ringworld vibes

Reminds me of The Unwritten: Stairway to Heaven - https://the-unwritten.fandom.com/wiki/The_Unwritten_(Volume_1)_Issue_24

A bunch of creatures go into an endless staircase that leads between worlds in an effort to find the top

In a pc game context I would try to make something like a no man's sky planet, but as you walk chunks of land in a radius around you get replaced with procedural new ones. something like a minecraft chunk loader that is relative to the player but wrapped around a sphere, and god forbid you actually want to have multiple players... Going into space can be more cursed but my favourite is: as you orbit the planet the active chunks scroll relative to your orbit with a speed relative to your distance; good fucking luck landing in the same place without insane math.