The Pentagon, located in Arlington, Virginia, is the headquarters of the United States Department of Defense. Often, the name "Pentagon" is used to refer to the Department of Defense itself. This massive office building is one of the largest in the world. Housing approximately 23,000 military and civilian employees, plus around 3,000 non-defense support personnel, it functions as a virtual city.
Construction on the Pentagon began on September 11, 1941, and was completed in January 1943 at a cost of approximately $83 million. The building was designed with five floors, two basement levels, and five concentric pentagons, or "rings," connected by 17.5 miles of corridors. Its innovative design allows one to walk between any two points in the building in roughly seven minutes. The Pentagon also contains eating and exercise facilities, as well as meditation and prayer rooms. The Hall of Heroes, located on the main concourse, is dedicated to Medal of Honor recipients. From 1998 to 2011, the Pentagon underwent a complete renovation to modernize the building and improve security.
