The Pentagon

The Pentagon is the five-sided headquarters of the U.S. Department of Defense in Arlington County, Virginia. Built in just 16 months under wartime pressure, it was completed on January 15, 1943. With roughly 6.5 million square feet of office space across seven floors, it was for decades the largest office building in the world. Despite its size, any two points inside are said to be reachable on foot within seven minutes thanks to concentric ring corridors connecting the five wedges. On September 11, 2001, American Airlines Flight 77 struck its western facade. Today access requires booking an official tour in advance; the Pentagon Memorial outside the security perimeter is freely visitable.