When a hallway curves in on itself, is it the same as when it just curves?
I'm positive that it's "curve in on itself", since the hallway is actually starting to curve as it is being said by one of the characters of this TV show.
My guess is that "to curve in on itself" means that the hallway kind of curls up. Unfortunately they don't follow the way any further.
If the hallway is on a slope, then I guess it could curve in on itself and would eventually be a spiral.
If it's flat, though, it can only curve around so far before it meets itself again.