City-ship

A city-ship is a mobile city used by the Ancients. With roughly the same internal space as is found on Manhattan island, it is one of the largest type of vessels ever encountered by the Tau'ri, with only Wraith Hive-Ships comparing in size.

Overview
The Ancients were using city-ships already several million years ago, when they departed Antarctica for the Pegasus Galaxy aboard the city-ship Atlantis. At least one other city-ship is known to exist in Pegasus; whether it was constructed there or was part ofthe Ancients' original migration is unknown.

A city-ships' design much more closely resembles a that of modern city than a spacecraft, with systems and living quarters distributed throughout several towers that extend away from the drive system; while in flight, the top of a city-ship would be considered the "front."

All known city-ships are capable of planetary landing; and indeed, they do not seem to have been designed primarily to function in space. Their hulls are not airtight, requiring the use of a shield to maintain atmosphere. As they are typically powered by three ZPMs, the shields are exceptionally powerful; though probably as a result of this, the hull itself is quite fragile.

As evidenced by Atlantis, city-ships are inherently buoyant, capable of floating on the surface of a large body of water without any apparent technological aid; they can also rest on the bottom of an ocean, though again the shield is needed to prevent flooding.

Some city-ships, such as Atlantis, contain their own Stargates, located near the top of the central tower so that it may be easily accessed by puddle jumpers. On other city-ships, however, this location instead houses the control chair, which in Atlantis is located in another tower altogether.

City-ships carry a large number of drone weapons, which are apparently their only armament. (The Atlantis Expedition did, however, install railguns on Atlantis for use as point-defense weapons against the Wraith.)

In addition, city-ships can host a myriad of other systems, many of which can be run without the need for a ZPM. However, most of the defensive systems, such as the drones and shield, cannot. The stardrive is designed to function with three ZPMs, but it is possible (if inadvisable) to fly the city with less. The Atlantis Expedition managed to do so with only one ZPM, albeit using additional energy supplied by an Ancient geothermal drilling platform.

List of City-ships

 * Atlantis
 * The Tower
 * Asuran city-ship