Washington, the Pintagone

The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia. As a symbol of the US Military, “the Pentagon” is often used metonymically to refer to the Department of Defense rather than the building itself.

The Pentagon is one of the world’s largest office building.It houses approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel. It has five sides, five floors above ground (plus two basement levels), and five ring corridors per floor with a total of 17.5 miles (28.2 km) of corridors. The Pentagon includes a five-acre (20,000 m²)
central plaza, which is shaped like a pentagon and informally known as “ground zero”, a nickname originating during the Cold War and based on the presumption that the Soviet Union would target one or more nuclear missiles at this central location.

source: wikipedia