The Blind Alcove

Through the arch is a room hardly bigger than the arch itself, and at its back a recess the size of a person is cut into the wall, with a step up into it. It goes nowhere. Whatever it was for, it was for standing in. The back of it is worn smooth at shoulder-blade height.

Depth 4.

You are reading the dungeon, not walking it. Rooms are only created by people, and only from inside the maze.