Cybertonium Pit

he Cybertonium Pit is a location deep within the planet Cybertron where the substance Cybertonium is mined for the Decepticons. Prisoners taken there are trapped within a circular force field, and guarded by a number of guards, under the leadership of the Head Guard. Of course, the Decepticons also bypass the memory circuits of any prisoners they take there, so none of them want to escape anyway.

The Transformers cartoon
After the Dinobots accidentally arrived on Cybertron through the space bridge, they were attacked by Shockwave's centurions who managed to capture all of the Dinobots except Swoop. Shockwave reprogrammed the Dinobots to be docile and placed them in the Cybertonium Pit to mine the substance for the benefit of Megatron's troops on Earth, who were suffering from Cybertonium depletion. When Spike, Carly and Swoop were also caught, they were banished to the pit. They were able to "fix" the Dinobots and stage a jailbreak, destroying all of the guards in the process.