With 620,000m2 of space and a height of 23.5 meters (77.1 feet), the Pentagon is the largest office building in the world. Built in 1943 and located in Arlington County, Virginia, across the Potomac River from Washington, D.C., the Pentagon is the headquarters building of the United States Department of Defense. With 5 surface floors and 2 basement levels, the Pentagon accommodates close to 26,000 workers (both military and civilian). Tne Pentagon is five-sided, with five ring corridors per floor stretching to about 28.2 kilometers of corridor length.