Secret Room under Snowbound

When playing Halo 3's Multiplayer map Snowbound with a friend on Forge, it is possible to glitch your way into a blue room hidden underneath a glass floor inside one of the bases.

Instructions (Turret Method)
To perform the glitch, a player must first overload the map with Trip Mines.

From there, they (Person A) must go to the base with a room under the floor. They will need to bring a friend (Person B) with them. The two will perform a variation of the Forge Turret Glitch.

Person A, in Edit Mode, should spawn a Plasma Cannon or an Machine Gun Turret and set it down. Person B, in Player Mode, should man the turret. At this point, Person A should grab the turret and turn it sideways, such that Person B is in between the turret and the floor. At this point, Person B should enter Edit Mode; they will find themselves beneath the glass.

Respawn Points can be placed in the room.

Instructions (Teleporter/Host Method)
This method requires two players to cooperate over Xbox Live; the two players will need to figure out which one of them is the "host". They can do this by simply attempting this glitch -- trial and error.

The player that is not host should spawn a Receiver Node and place it on the glass floor. They should then button-mash A until the Teleporter sinks beneath the floor. Once that is done, the player can spawn a Sender Node and use that to get in. This method works in other parts of Snowbound, including the Ghost/Mongoose spawn point.