An outdoor memorial dedicated to the Pentagon victims of 9/11 opened in 2008. Following the attacks, the western side of the building was repaired, with a small indoor memorial and chapel added at the point of impact. It was the first significant foreign attack on Washington's governmental facilities since the city was burned by the British during the War of 1812. Five al-Qaeda hijackers flew American Airlines Flight 77 into the western side of the building, killing themselves and 184 others: 59 on the airplane and 125 in the Pentagon. In 2001, the Pentagon was damaged during the September 11 attacks.

The central five-acre (2.0В ha) pentagonal plaza is nicknamed ' ground zero' on the presumption that it would be a prime target in a nuclear war. It has five sides, five floors above ground, two basement levels, and five ring corridors per floor with a total of 17.5В mi (28.2В km) of corridors. Some 23,000 military and civilian employees, and another 3,000 non-defense support personnel, work in the Pentagon. The Pentagon is the world's largest office building, with about 6.5В million square feet (150 acres 60В ha) of floor space, of which 3.7В million square feet (85 acres 34В ha) are used as offices. Army Corps of Engineers, which supervised it. General Brehon Somervell provided the major impetus to gain Congressional approval for the project Colonel Leslie Groves was responsible for overseeing the project for the U.S. Ground was broken on 11 September 1941, and the building was dedicated on 15 January 1943. Located in Arlington County, Virginia, across the Potomac River from Washington, D.C., the building was designed by American architect George Bergstrom and built by contractor John McShain. military, the phrase The Pentagon is often used as a metonym for the Department of Defense and its leadership. It was constructed on an accelerated schedule during World War II. The Pentagon is the headquarters building of the United States Department of Defense.

Pentagon web monitor