Cybertron before it was critically damaged
Cybertron is the home planet of the Transformers, and is located roughly ten thousand light years away from Earth, the home planet of Humans. Cybertron is a planet made entirely out of metal, from its surface to its core and even to its inhabitants.
Cybertron itself was razed during the Cybertronian Civil War, in which the Autobots, led by Optimus Prime, went to war against the Decepticons, ruled by Megatron. Cybertron itself was almost completely destroyed during this war but once the Autobots and Decepticons had left the planet it began to rebuild.