THE STARGATE OMNIPEDIA
CITY SHIP, ANCIENT
The greatest technological marvel known to have been created by the Ancients, the city ship is a snowflake-shaped behemoth, stretching kilometers in diameter. Capable of intergalactic travel via a powerful star drive, at least one of these craft crossed the 3.5 million light year gulf between the Milky Way and Pegasus Galaxies.

Though Atlantis is believed to have been considered the crown jewel of Pegasus, she was not alone. Perhaps this suggests that Atlantis was the first in a line of city ships. What is certain is she was the central nexus for all Ancient activity in the Pegasus Galaxy, and therefore their last line of defense from the Wraith.

A second city ship was discovered by the Atlantis expedition on Eldred's planet, its vastness shrouded by the crust of the planet, as tens of thousands of years of growth had buried the massive craft.

USED BY - Ancients, humans, Eldred's people
FIRST APPEARED - Rising

KEY EPISODE(S) -
Rising, Part 1 - Several million years in the past, the Ancients launch Atlantis from the surface of the Earth and fly the city ship to a new home in the Pegasus Galaxy.
The Tower - Sheppard's unit discovers that Atlantis was indeed not alone. Its sister city is discovered on Eldred's planet.