The Raven Rock Mountain Complex (RRMC), also known as Site R, is a U.S. military installation with an extensive underground nuclear bunker located near Blue Ridge Summit, Pennsylvania. Built in the early 1950s during the Cold War era, this facility was designed as a secure relocation site for the U.S. government in the event of a catastrophic nuclear, chemical, or other devastating attack. Often referred to as an "underground Pentagon," the complex contains emergency operations centers for the United States Army, Navy, Air Force, and Marine Corps.
The bunker represents one of the most extensive government survival measures undertaken during the Cold War period.