While technically not a room (although some still consider it to be), it is a narrow, slide-like passage that connects the Quicksand Bog to the Room of the Secret Password. Players could slide down the tunnel from the top, or climb up from the bottom.
Trivia
The slide used for the Pharaoh's Secret Passage is the twisty part of the Sundae Slide from Double Dare.
The "DANGER" sign was given away as a prize in the first season of the game show Figure It Out.
In the CW reboot, a similar access called the Ladder of Death was used. Much like the passage, it was not technically a room, but a way that connected two rooms.