Science Fair Project Encyclopedia The Pentagon is the
headquarters of the United States Department of Defense. It was
dedicated on January 15, 1943 and it is the world's largest
office building. Those who work within its walls often simply
call it "The Building", "Fort Fumble" or the "Puzzle Palace".
The building is pentagon-shaped in plan and houses approximately
23,000 military and civilian employees and about 3,000 non-
defense support personnel in Arlington, Virginia, just outside
Washington, DC. It has five floors and each floor has five ring
corridors. Built during the early years of World War II, with
construction supervised by the future Manhattan Project
supervisor Leslie Groves, it is still thought of as one of the
most efficient office buildings in the world. Despite 17.5 miles
(28 km) of corridors it takes a maximum of seven minutes to walk
between any two points in the building. It was built from
680,000 tons of sand and gravel dredged from the nearby Potomac
River that were processed into 435,000