Rope is the best one I can think of that doesn't have any kind of caveat. It takes place within an apartment, set across three connected rooms (kitchen, hallway, living/dining area) and the scenes are even stitched together in such a way that it gives the impression of being shot in a single take.

Rear Window is close, but it does leave the apartment at least once. One could also argue that the binoculars scenes are taking the viewer to a different location.