In the 1974 rough draft, the spaceship which the heroes steal from the Aquilae spaceport is parked vertically in an underground hangar. Although the spaceship itself is standing on one end, the internal structure features a corridor running down the length of the ship horizontally, apparently using artificial gravity oriented 90 degrees out of kilter with the planet surface.
A similar subtle use of a 90-degree reorientation of gravity is seen on the gun turrets of the Millennium Falcon in the final film.
The spaceship being parked vertically, with its engines pointing downward, is obviously evocative of the Apollo moon rockets, although its hangar is more reminiscent of a Cold War missile silo, complete with cover plate.
Various making-of books for TPM suggest that Lucas originally wanted to feature an underground city on the desert planet in the first film. Presumably this actually refers to the subterranean spaceport of the rough draft.