Trodos

Trodos was a human colony world.

History
In 2066, MacTaggart constructed the Trods to give himself power over the other colonists and used them to enslave everyone. When the First Doctor, John and Gillian arrived on Trodos, they deactivated the Trods and freed the slaves. (TVC: The Trodos Tyranny)

Some time later, a space traveler came to Trodos and reactivated the Trods. (TVC: Return of the Trods)

Centuries later, the Daleks invaded Trodos and massacred most of the Trods, but were defeated by the Second Doctor. (TVC: The Trodos Ambush)