See a Massive, Self-Sufficient Military Complex Inside a Mountain

The North American Aerospace Command (NORAD)'s clandestine Cheyenne Mountain Complex in the Front Range of the Rocky Mountains near the city of Colorado Springs is one-of-a-kind in terms of its scope and its role as the fortified home of the US defense arsenal's most advanced tracking and communications equipment.

The Cheyenne complex includes 15 three-story underground buildings; each is buffered by a 25-ton blast door. The buildings are mounted on massive springs to absorb the shock from a possible nuclear blast, while the entrance is protected by a vault-like door several feet thick.

The bunker is home to more than 1,000 personnel, and it is able to operate as an underground town for months with its own supplies of fresh water and food.

The complex is 2,000 feet below the granite surface of Cheyenne Mountain and designed to withstand a direct hit by a 30 megaton nuclear explosion. It was shut down in 2006, but re-opened in 2015.

A joint US and Canadian command, NORAD was formed back in the 1960s in order to scan the skies for threats emanating from missiles, aircraft and space objects.