Habitation sphere

A habitation sphere was a large artificial orbital structure designed to house large numbers of people. According to a report by Pollux Hax, two giant-sized habitation spheres were constructed in orbit of Imperial Center by the planet's great space construction platforms during the reign of the Galactic Empire.

Behind the scenes
The artwork depicting the habitation spheres was originally concept art for an early story for Episode VI: Return of the Jedi, in which two Death Stars were being built in orbit of the capital planet of Had Abbadon. As a result, one of the habitation spheres even has the recessed dish on its southern hemisphere where a superlaser would be located.

The manner in which Pollux Hax discusses the spheres, insisting that they are being assembled "strictly for peaceful purposes," suggests the possibility that just the opposite is true - that these may have in fact been further Death Stars early in the process of being built. This supposition is often cited as a source for a third Death Star depicted in the Star Tours ride.