The Pentagon, headquarters of the Department of Defense, is one of the world's largest office buildings.

The building was constructed in 16 months and completed on January 15, 1943 at an approximate cost of $83 million. The original site was nothing more than wasteland, swamps and dumps

Approximately 23,000 employees, both military and civilian, work in the Pentagon offices that occupy 3,705,793 square feet.

Despite 17.5 miles of corridors it takes only seven minutes to walk between any two points in the Pentagon building