@eniko I experimented with this on Duke3D because the build engine was "2d" but as long as you arranged your physically overlapping regions to not be visible at the same time, it didn't care about spatial constraints. There's a level (in an expansion, IIRC) that has a 720º circle using this approach.
I used it to have things like a pillar in a hallway that, as you passed it, you'd see there was a hallway within it that went off at a right angle to the hallway you were in. It wasn't TOO disturbing to look at, but it was obviously impossible.
The absolute relations couldn't change, though, so you couldn't have a 50 foot long hallway through a 1 foot thick wall or stuff like that, though.
So, if you could include that sort of thing, probably go with "amazing"?