"Stargate Atlantis" is a science fiction television series that premiered in 2004 as a spin-off of the popular show Stargate SG-1. The series follows a team of explorers who travel to the lost city of Atlantis, located in the distant galaxy of Pegasus. They encounter various alien species and face numerous challenges while trying to protect their home and uncover the secrets of the ancient city. The main characters include Dr. Elizabeth Weir, John Sheppard, and Rodney McKay, who work together to explore new worlds and defend against threats like the Wraith, a powerful alien race. The show combines adventure, science fiction, and team dynamics, appealing to fans of the genre.