The whole canyon is wider at the top and narrower at the bottom. Makes sense for structural purposes- either that or some sort of empire-state-building-esque steppe architecture. It's also a left-over from the original '05 design that I really don't have the time or effort to change. :P Every doorway on the map aligns with it, and even though it would be easier to make new doors if I fixed them all, that would take forever.

Oh, and if you didn't see, I updated the post above with a better view of the wall.