The Cheyenne Mountain Complex is a hardened military installation located inside Cheyenne Mountain in El Paso County, Colorado. Built during the Cold War as a secure command center, it serves as an alternate command center for the North American Aerospace Defense Command (NORAD) and the United States Northern Command (USNORTHCOM). The facility was designed to withstand nuclear attacks and continues to operate as a training complex for crew qualification.
Its construction followed more than 11 previous US command bunkers, making it one of the most advanced underground military facilities in the United States.