A top-secret U.S. government facility at Nellis Air Force Base in the Nevada desert. Area 51 serves as a repository and research station for many of Stargate Command's acquisitions, where alien technologies can be studied, reverse-engineered, and stored.
Touchstone - SG-1 visits Area 51 to ensure that the Touchstone, an alien weather-control device, has not fallen into their hands.
Smoke and Mirrors - Samantha Carter visits Area 51 to make a visual inspection of the alien mimic devices, only to discover that they've been stolen.
Enemy At the Gate - Shortly after Earth officials move the Ancient weapon from Antarctica to Area 51, Wraith Darts crash into Area 51 in a kamikaze run, destroying the control chair.