Stardrive

Atlantis, being a spaceship in-and-of itself, possesses its own fully-functioning sublight engine and hyperdrive. The stardrive allows Atlantis travel to diffent planets, and even distant galaxies, in only a matter of days. The stardrive requires an incredibly large amount of power and so can only be activated if there are three Zero Point Modules powering the city, however Dr. McKay and Colonel Sheppard have powered the stardrive using only one ZPM, with the drilling platform adding a little more power to get it in the air, though they dropped out of hyperspace far too early. Atlantis, like all other city-ships, doesn't possess a hull in the traditional sense, instead having an atmosphere that can only be contained by the city's shield.