The Underground Bunker is an underground city on the Genii homeworld that the Genii live the majority of their lives. The bunker and tunnels were built one thousand years ago by Genii's ancestors as protection from war. But the bunker was forgotten and during the year 1004 when the Wraith attacked the home planet a few survivors sought shelter in the bunker, and since then they have developed a technological civilization in secret from Wraith to protect themselves. The bunker has been built through centuries of military training, research labs and military headquarters and residences. There are several nuclear reactors in the bunker that gives power and Genii develop their nuclear bombs for use against the Wraith.
Major John Sheppard and Dr. Rodney McKay discovered the Bunker after detecting Radiation. (SGA: "Underground", "The Storm", "The Brotherhood", "The Siege, Part 2", "Coup D'etat")