"More Disney That Never Was"
PCU:
The first is a rare glimpse of Atlantis Encounter, an attraction once proposed for the area in Disneyland’s Tomorrowland currently occupied by the Autopia. This attraction is famous for the brief few days in 2001 or so when Imagineers put up signs around the Disneyland sub lagoon hinting that a new attraction based on Atlantis was on its way.
...
Another treat is this look at the model of the Lucas Spaceport, an early attempt at a Star Wars themed area for Tomorrowland. This would have converted the Carousel of Progress complex into an enormous spacecraft.