America's Book Of Secrets: The Pentagon http://youtu.be/tQCLxpp4TTQ
It is the epicenter of America's military operations... a five-sided fortress with a single purpose--to defend the United States and its citizens. But behind the concrete walls and re-enforced windows are secrets. Enter the headquarters of the U.S. Department of Defense and explore the complex operations and top-secret business conducted at the largest low-rise office building in the world.