File:Quake II Receiving Center Lava Puzzle.png

From Quake II, PC version, the floor of this room in the Receiving Center level is a lava pool when you enter via the red pipe on the right. To reach the exit pipe, kill a Guard, press a button, cross a bridge, kill a Gunner, operate a lever, kill another Gunner, press another button, ride a lift platform to the now-open cover and there you are.