#Dungeon23 Tomb of the Vampire Queen, Level 2, Room 20

This door looks like it leads to another guard room (like 19 before it).

 The floor of this room is trapped. If a pressure plate is stepped on the floor gives way and all occupants slid down (away from the door) to the next level below.

A thief can find this trap, but not disable it. They can however avoid it.