So far to me, the level design in Dark Souls stands out as some of the most unique and aesthetically awesome I've seen in ages. Thing is, I'm not sure it ended up that way on purpose; much of the layout seems as if From Software sketched and laid out everything spatially as much as their crazy brains would allow, but in a very modular fashion. Every room, platform, and hallway piece by piece seperately, then stitched them all together into one long insane universe, then designed the actual architecture and geography of the world to justify the pre-existing layout. The end result feels like something that's just shy of anything in reality, with barely any symmetry or focus, chaotic with just enough resemblance to the way people would actually design buildings. This adds immensely to the feel of the game, because not only am I always slightly uneasy, but I've never even thought of needing a map because everything's been burned into my subconscious as I see it.

It's very reminiscent of what I've always imagined the city of R'lyeh to look like: http://en.wikipedia.org/wiki/R'lyeh

Non-Euclidean geometry in games. Whaddya guys think...great or super-great? Any other examples of stuff like this?

There needs to be more games like Culdcept Saga and Magic the Gathering on XBLA.  So, so many hours wasted.  I'd write more, but I need to get more cards...(sigh).