A Gravitation chamber is a small room capable of producing artificial gravity, effectively making the wall opposite the door the floor. This ability may be turned on or off; when off, one may enter the room normally. By turning the artificial gravity on once someone has entered the room, the room functions as an exit-less prison.
An arrow on the wall rotates to point towards the room's "floor".
When Jack O'Neill was imprisoned and tortured by Ba'al, he was kept in a Gravitation chamber between interrogations, where he was kept company and comforted by the ascended Daniel Jackson. (SG1: "Abyss")