Pentagon

The headquarters of the US Department of Defense, Arlington, Virginia from 1947, situated on the Potomac River opposite Washington, DC. One of the world's largest office buildings (five storeys high and five-sided, with a pentagonal central court), it houses the administrative and command headquarters for the US armed forces and has become synonymous with the military establishment bureaucracy. In September 2001, as part of a coordinated terrorist attack on the USA, the Pentagon was severely damaged when a hijacked aircraft was crashed into its northwest wall, bringing part of the structure down and killing 126 people.

The budget for the Pentagon's intelligence services covers the National Security Agency, which conducts electronic eavesdropping; the National Reconnaissance Office, which builds spy satellites; and the Defense Intelligence Agency, which manages Pentagon intelligence.

The building contains 27 km/17 mi of corridors, and possesses the largest private branch telephone exchange in the world.

Reconstruction of the Pentagon following the September 2001 terrorist attack cost around US$500 million and was completed in 2003.

The Pentagon Papers were classified documents published by the US press 1971 on US involvement in Vietnam.

pentagon

Five-sided plane figure. A regular pentagon has all five sides of equal length and all five angles of equal size, 108°. It has golden section proportions between its sides and diagonals. The five-pointed star formed by drawing all the diagonals of a regular pentagon is called a pentagram. This star has further golden sections.