'E' Ring offices are the only ones with outside views and are generally occupied by senior officials. The concentric rings are designated from the center out as 'A' through 'E' (with additional 'F' and 'G' rings in the basement). The south parking lot adjoins the southwest façade, and the west side of the Pentagon faces Washington Boulevard. There is also a concourse on the southeast side of the second floor of the building, which contains a mini-shopping mall. The main entrance for visitors is on the southeast side, as are the Pentagon Metro station and the bus station. A stepped terrace on the River Entrance leads down to the lagoon and a landing dock was used until the late 1960s to ferry personnel between Bolling Air Force Base and the Pentagon. The River Entrance, which features a portico projecting out twenty ft (6 m), is on the northeast side, overlooking the lagoon and facing Washington. On the north side of the building, the Mall Entrance, which also features a portico, leads out to a 600 ft-long (180 m) terrace that is used for ceremonies. Starting with the north side and moving clockwise, its five façade entrances are the Mall Terrace, the River Terrace, the Concourse (or Metro Station), the South Parking, and the Heliport.

The Pentagon building spans 28.7 acres (116,000 m 2), and includes an additional 5.1 acres (21,000 m 2) as a central courtyard. 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 federal facilities in the capital area since the burning of Washington 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 other people: 59 on the airplane and 125 in the Pentagon. In 2001, the Pentagon was damaged during the September 11 attacks. About 23,000 military and civilian employees work in the Pentagon, as well as about 3,000 non-defense support personnel. 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, with a central five-acre (2.0 ha) pentagonal plaza. The Pentagon is the world's second largest office building, with about 6.5 million square feet (600,000 m 2) of floor space, of which 3.7 million square feet (340,000 m 2) 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. 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, in Arlington County, Virginia, across the Potomac River from Washington, D.C.

Inside office building