Deep beneath a Pennsylvania mountain lies the Pentagon's secret, hardened underground backup facility.

Countries & Cities · Published 3 October 2026 Swipe more like this →

In short: Known as Site R or the underground Pentagon, the Raven Rock Mountain Complex was built to ensure the survival of U.S. military leadership during a nuclear attack. This massive, fortified facility remains a critical, highly restricted node in the nation's continuity of government plans, hidden away from the public eye.

Construction of the facility began in 1951, following a federal petition to seize land in Pennsylvania for a protected Cold War communications center. By 1954, development of the site, often called the Little Pentagon, had cost $35 million. The complex was designed to serve as an Alternate National Military Command Center, providing a hardened bunker capable of withstanding nuclear blasts, with blast resistance reaching approximately 140 psi by 1963.

The facility functions as a hub for the U.S. military, housing emergency operations centers for the Army, Navy, Air Force, and Marine Corps. It is managed by the 114th Signal Battalion and supported by the Defense Information Systems Agency, which provides essential computer services. The site's strategic importance was underscored during the September 11, 2001, attacks, when high-ranking officials, including Vice President Dick Cheney and Deputy Secretary of Defense Paul Wolfowitz, were moved to the complex for protection.

Despite its real-world role as a secure government installation, Raven Rock has become a fixture in popular culture, appearing in numerous films, novels, and video games. These fictional portrayals often depict it as a sanctuary for government elites or a base for resistance movements. In reality, the site remains a strictly controlled military reservation, and since 2007, federal policy has explicitly prohibited unauthorized photography or mapping of the complex, reinforcing its status as one of the most secretive installations in the United States.

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