What if the world was not a sphere but instead a donut? This article answers some of those questions. And the possibilities sound really interesting.
Obviously, the author thought so. His 'Summary' is this:
"Torus-worlds are unlikely to exist naturally. But if they did, they
would make awesome places for adventure. A large surface area. Regions
with very different climate, seasons, gravity and ecosystems. Awesome
skies on the interior surface. Dramatic weather. Moons in strange
To be honest, when I think about this for use in fantasy gaming, I'm not sure that the player characters would ever have reason to know what the shape of their world was. It wouldn't matter to them (unless it was a Spelljammer type campaign) OR the world would seem flat to them, just like another world that we all know pretty well.
But for that brand of DM/GM who likes to know why things are the way they are in his or her world, a torus-world would allow crazy climates, strange (to us) night-day patterns, a very interesting sky with bizarre moon motions, among other things. It would truly seem fantastic, AND the DM could explain it all.