Zactus

Zactus was a planet which had two regions: a warm region with active volcanoes which was inhabited by dinosaur-like creatures and the Zactions, and a cold region inhabited by robots led by the chief robot. The First Doctor visited Zactus' warm region and met the Zactions, while an astronaut visited the cold region and was captured by the robots. The Doctor met the robots and secured the astronaut's release before departing. (PROSE: Dr Who on the Planet Zactus)