establishes much of the backstory of Atlantis: The city was built by the Ancients millions of years ago, originally as a central outpost in prehistoric Antarctica, until an unexplained crisis—involving a virulent plague—forced them to relocate the city to the planet Lantea in the Pegasus Galaxy via intergalactic hyperdrive engines. The Ancients (known as "Ancestors" to the denizens of Pegasus, and "Lanteans" to the Wraith) seeded several human populations in the Pegasus galaxy, but rarely interbred with them. As explained in season 1's "The Defiant One", the Wraith drove the Ancients from their holdings until only Atlantis was left, defended by its powerful shield and a network of armed satellites. The Atlantis Expedition learn during their arrival in Atlantis in "Rising" that the Ancients submerged the city in Lantea's ocean to evade detection by the Wraith and returned via stargate to Earth, where survivor recollections formed the basis for the ancient Greek accounts of Lost City of Atlantis. In the Atlantis series finale "Enemy at the Gate", Atlantis returns to Earth and lands in the Pacific Ocean near San Francisco. The producers intended the city of Atlantis to be the size of Manhattan. Many sets used for Atlantis are part of a large sound stage that was built for almost US$2 million. This stage is used for rooms like the brig, several balconies, and other interior parts of Atlantis. Green screens were used if an outdoor view was required in an episode. According to digital effects artist Bruce Woloshyn, the series' original CGI model of the city of Atlantis was over four million polygons, which was feature film in size. This allows the city model to still look good and detailed in extreme close view. Since most of the city is modelled rather than textured, the details appear more realistic when the virtual camera revolves around the city model. Wraith The Wraith are the main antagonists in Stargate Atlantis and the dominant species in the Pegasus Galaxy. They are biologically immortal hive-based humanoids who maintain the human worlds of the Pegasus Galaxy as livestock to feed on their "life-force". As established in season 1's "The Gift", the Wraith evolved in the Pegasus galaxy after a human population seeded by the Ancients was fed upon by an insect called the irratus bug, which has the ability to draw upon a human's life to heal itself. As they fed, the bugs incorporated