The full size exterior spaceship set is in Stage 1 and only consist of the front facade and just a small part of the interior. The alien planet set has a painted cyclorama that goes around three walls, with two rock walls that roll away for drive in access so the space van can drive across the sets.
The main interior of the spaceship is on another stage. Although mostly built with plywood electrical panels, there are a few original prop panels that were once used in actual 1960s television shows and movies. Some of them were once actual early computer and military equipment that, when they became obsolete, were bought as surplus and turned into props by the Hollywood prop departments. Hollywood liked them because they had a lot of lights that flashed and made it look like the computers were actually doing something.
The ancient ruins and cave set is in Stage 2.