The Gravity Room is a metal chamber like room created for the purpose of sparing in increased gravity for added effects. It increased gravity by multiplications of the Earths gravity.
Ed,Edd N' Eddy ZEdit
It was first created by Tails and Edd in order to create a suitable training environment to prepare the heroes for the upcoming showdown with Chaos. It originally had a limit of times 20 Earths gravity.
By the time of the Revenge Saga, this limit had been increased to times 50. It was increased to 100 times through the energy of the Chaos Emeralds in order to battle the robotic creations of Dr. Eggman and Proffesor Utonium.
A year later the limit had been brought up to times 125 Earths gravity, a suitable training ground for the Saiyans to master their False Super Saiyan transformations. After this proved not enough however, the chamber was increased to 300 times.