Once upon a time, a highly developed and advanced race, the Ancient, used the Earth as their base. Millions of years ago, for unknown reasons, they left the Earth and went somewhere, leaving only an outpost in Antarctica. After General Jack O'Neill used an Ancient weapon from the outpost to destroy the fleet of the Goa'uld that came to attack the area, the countries cooperated to establish the Antarctic Alliance to study the Ancient technology in the outpost and promote international cooperation and peace. During the research process, they discovered the place where the Ancient went after leaving the Earth - the Pegasus Galaxy. Therefore, in order to discover the buried history and explore the unknown world, the countries formed the Atlantis expedition team and reached the city of Atlantis that flew away from the Earth millions of years ago through the interstellar gate. But unfortunately, the arrival of the Earthlings awakened a group of monsters that ruled the Pegasus Galaxy - the Wraiths. They were technologically advanced, physically strong, rude and brutal, unfaithful, and used humans as livestock and sucked people's lives. Ten thousand years ago, they defeated the Ancient and forced them to flee back to Earth, and the expedition team also discovered an astonishing fact: Wraith was the product of Ancient's experiment! In order to fight against the powerful Wraith, the Atlantis team had to explore the planets of the Pegasus galaxy, contact the natives of Pegasus, and try to find a way to resist Wraith, going through a series of dangerous journeys. [PS] "Stargate Atlantis" (SGA) started as a spin-off series of Stargate SG-1. SG-1 was originally going to continue its seventh season and the second feature film, but when SG-1 was in its eighth season, the scheduled movie became a two-episode season finale "Lost City", and the setting of Stargate Atlantis was also moved to the Pegasus galaxy. [10] This allows the two programs to coexist in the same fictional universe, and then the two programs even begin to connect with each other, basically realizing the audience's desire to watch two programs at the same time. This program was produced by most of the original SG-1 crew in the same studio. Atlantis premiered on the Sci-Fi channel on July 16, 2004, starring en:Joe Flanigan and en:Torri Higginson, with Rainbow Sun Francks, en:David Hewlett and en:Rachel Luttrell in supporting roles. Hewlett and Higginson previously had roles in SG-1. In the second season of Atlantis, en:Paul McGillion and en:Jason Momoa (replacing Francks) joined the regular cast. The series ended in its fifth season.