Postcard USA, Washington D.C. - The Pentagon aerial view
The Pentagon is the headquarters of the United States Department of Defense.
The Pentagon is one of the world's largest office buildings, with about 6,500,000 sq ft (600,000 m2), of which 3,700,000 sq ft (340,000 m2) are used as offices. Approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel work in the Pentagon. It has five sides, five floors above ground, two basement levels, and five ring corridors per floor with a total of 17.5 mi (28.2 km) of corridors.