Atlantis, also called the City of the Vespers is a city-ship built by the Germans/Hydra on April 15, 2013 and has approximately the same internal space as found in Manhattan. It is the second largest Vesper base in the world.
Atlantis has a great deal of advanced technology in it, ranging from the Stargate and Puddle Jumpers, to Drone weapon, the Stardrive and the all-important shield. Atlantis's main energy supply are Zero Point Modules, which are stored in a special room. To gain access to all of the technology and features of Atlantis, three are needed, however in cases of emergency, one can perform the most important tasks. The city also possesses several solar-powered generators, however they don't provide much energy in proportion to the massive amounts required to operate any useful technology in the city. In one extreme instance, lightning strikes from a massive storm were used to briefly power the shield in order to save it from a tsunami in a test. A more effective method of alternatively powering Atlantis comes in the form of a geological drilling station located on the sea floor
The shield of Atlantis is a massive dome that completely encompassed the city when activated. It protects the city from anything ranging from orbital bombardment, to the weight of an entire ocean, to a tsunami, to Coronal mass ejections, to falling space debris. The shield can cover the city like a skin to prevent the ocean from crashing inside when the city is submerged, or to prevent air evacuation when traveling through space. Also, the shield can be expanded when necessary to protect nearly an entire planet, or contracted to save power. The shield can also be used to cloak the city.
The Stardrive on Atlantis enables the city to travel to distant planets, or even galaxies, in only a few days and is incredibly powerful. It is designed to operate with 3 Zero Point Modules, but can be powered by 1 if the situation calls for it, and if other power sources are used as well, the Mobile drilling platform for example. The most power is used in getting Atlantis off the surface, after this a single ZPM is able to power the city and open a hyperspace window.
The Stargates are a series of devices, built by the Germans/Vespers, that create artificial subspace wormholes, allowing for near-instantaneous transportation between two distant points in space. The Stargates are often considered to be the Germans' greatest creation.