I did not know that yesterday!

Suprisingly, the Department of Defense (DoD) is fairly forthcoming about their headquarters. The Pentagon is one of the world's largest office buildings -- it houses over 26,000 employees and boasts 17.5 miles of corridors.

Yet, despite its enormous size, "it takes only seven minutes to walk between any two points in the building." Brigadier General Brehon B. Sommervell, Chief of the Construction Division of the Office of the Quartermaster General, ordered the neo-classical building as a temporary solution to the War Departments critical shortage of space. Built in an amazing 16 months, the Pentagon cost $83 million (an investment returned within 7 years), consolidated 17 War Department buildings, and opened for business January 15, 1943.

Although the DoD doesn't mention how the shape of the building was determined, they do provide a handy link to the Defense Technical Information Center web site, which fills in the blanks: "The original site chosen for the Pentagon was a tract of land known as Arlington Farms. The site was bordered by five roadways thus dictating the
concept of a pentagonal shaped building."

While President Roosevelt later ordered the building moved to a different location, the original design concept -- "an open air court surrounded by five concentric pentagonal rings (or corridors) traversed by ten spoke-like corridors" -- was retained.

Perhaps not coincidentally, the pentagon symbol is linked with the planet Venus, often associated with warfare, and is also a basic design for fortresses.

If you're interested in further exploring the enigmatic building, the Pentagon offers tours, or you can take a virtual stroll around the building.