Council Citadel

Standing above its surroundings in the capital city of Cybertron, the Council Citadel served as the meeting place for the Maximal Elders.

Beast Machines cartoon
After "purifying" Cybertron, Megatron made it his base of operations, turning the meeting room into his throne room (although he was technically part of the ceiling).

It was also where he originally kept the sparks of the kidnapped Transformers.

During the Vehicons' assault on the big floating head, it crashed into the Citadel after losing all its power, but without damaging the Citadel itself. Some things are built to last.