The Pentagon, Arlington, Virginia, Headquarters for the Department of Defense

The Pentagon, which is located in Arlington, Virginia, is the official headquarters for the Department of Defense. The neoclassical building replaced the 17 buildings that were once used by the War Department.

The Pentagon, which was designed by architect George Bergstrom, was built in only 16 months at a cost of around $83 million. It was completed on January 15, 1943. At most, the building housed 33,000 workers. Today, 23,000 people, both military and civilian, report to work at the Pentagon each day.

Until January of 2008, The Pentagon, which sits across the Potomac River from Washington D.C., held the record for the building with the most square feet in the United States. A building in Las Vegas was built that has over 30,000 more square feet than The Pentagon. Still, The Pentagon remains one of the largest office buildings in the world.

There are 3,705,793 square feet of office space and over 17 miles of hallways contained in the five "wedges'' that make up the building. There are five floors and two basement levels. There is also a five acre courtyard in the center. There is a state of the art gym and several dining options within The Pentagon as well.

Interestingly, because the building was built during World War II, no marble was used. That is because marble is imported from Italy, a country that was an enemy during that war.

The Pentagon was attacked on September 11, 2001 when terrorists flew American Airlines Flight 77 into the building. Sadly, 125 Pentagon employees were killed in the attack. Repairs to the building cost close to $500 million.

Tours are free to the public and are available by reservation only. Most visitors agree that taking a tour is worth is even if only for the novelty of being able to visit the building where so many decisions that have had a huge impact on the country have been made.

A visitor from Philadelphia said, "I'm not sure what the tour would have talked about pre-9/11 because 40% of the talking points were about the damage to the building, etc. Still very interesting and the memorial room is quite touching.'' Some visitors said they arranged the tours through their State Senator's office.

Visitors planning to take a tour should become acquainted with the strict security guidelines that govern all visitors to The Pentagon. Tours are not given on weekends or on any Federal holidays. Those wishing to reserve a tour should do so as far in advance as possible.