The Cold Drain
The passage is narrow enough that your sleeves brush the green on both sides. It runs on for some 3 paces, straight, and no wider than you could reach across. A boat — if it was a boat — has rotted to a rib-cage of grey wood against the far wall. Something small goes quiet when you enter, and stays quiet.
Depth 7.
You are reading the dungeon, not walking it. Rooms are only created by people, and only from inside the maze.