The Hyperbolic Time Chamber ("Room of Spirit and Time") is a endless dimension that can be accessed through a special door on the Lookout.
Once inside, time slows down and while one day passes in the outside world, an entire year goes by in the Chamber. Inside, the air is dense, the temperature fluctuates wildly and the gravity is greater than Earth's. Outside of the protection of the door and living quarters is an endless expanse of nothingness.
The Chamber is used by the Z-Fighters to train and grow in strength in short periods of time.