So I am more of a table-top gamer than a writer (though I write a fair amount of short stories that take place in the work-in-progress world I have designed). In trying to fine-tune the actual cosmology of the world (there's plenty of differing creation myths based on culture, but the theme of the game is finding the actual truth) it seemed to make sense, given all the other stuff involved, to attempt to make the world actually flat (or more accurately, a flat disc inside of a sphere not unlike the structure of a gyroscope).
Now the players all assume the world is round. I'm not looking at making it scientifically perfect in regards to things like gravity and seasons (it is fantasy after all), but what other subtle differences could I sprinkle about as clues (at least until the player-characters discover and dissect the ancient astrolabe puzzle thing that shows the total "unification" of the cosmos and gods) that the world isn't actually round? What are some scientific implications of such a place that I might toy with?