Deep inside the granite heart of the Rocky Mountains, shielded beneath 2,000 ft of solid rock, lies one of the most secure, most resilient military installations ever constructed by the United States: the Cheyenne Mountain Complex. Built in the early years of the Cold War, during a time when nuclear weapons were reshaping the nature of global security, Cheyenne Mountain was designed to survive the unthinkable — a direct nuclear strike — and continue operating even in the aftermath of total war. This mission: aerospace defense, early missile warning, nuclear detection, and the coordination of continental airspace security, has made Cheyenne Mountain a cornerstone of North American defense architecture for more than half a century.

Source: America’s Nuclear – Proof Mountain That Can Survive Doomsday