The Pentagon , located in Arlington , Virginia , serves as the headquarters of the United States Department of Defense . It is a symbol of the U.S. military . The Pentagon is also the world’s largest office building by floor area, with about 6,500,000 sq ft (604,000 m2), of which 3,700,000 sq ft (344,000 m2) are used as offices . The Pentagon houses a daily working population of approximately 24,000 employees, both military and civilian.
The building was constructed in the early years of World War II in tonly16 months, and was completed on January 15 , 1943 at a total cost of almoust $83 million. Its construction managed the consolidation of 17 buildings belonging to the War Department, and required 5.5 million cubic yards of earth, 41,492 concrete piles, as well the dredging of 680,000 tons of sand and gravel into 435,000 cubic yards of concrete.
The exterior walls of the concentric rings and the interior courtyard are exposed concrete. They appear to have a wood-grain texture because they were poured into wooden forms made of 8-inch boards. Clockwise from its northern point, the Pentagon’s five facades are the Mall Terrace Entrance facade, the River Terrace Entrance facade, the Concourse Entrance (or Metro Station) facade, the South Parking Entrance facade, and the Heliport facade. The outer facades of the Pentagon are simple, with a minimum of ornamental embellishment. Although the ornamentation style is classical in origin, it has been greatly simplified. The outer walls are limestone, as a direct result of a restriction by President Roosevelt that there be no marble in the building.
It has five sides, five floors above ground (plus two basement levels), and five ring corridors per floor with a total of 17.5 mi (28.2 km) of corridors. The Pentagon includes a five-acre (20,000 m²) central plaza, which is shaped like a pentagon and informally known as “ground zero”, a nickname originating during the Cold War and based on the presumption that the Soviet Union would target one or more nuclear missiles at this central location in the outbreak of a nuclear war.
September 11 attacks
On September 11, 2001, hijacked American Airlines Flight 77 crashed into the western side of the Pentagon, killing 189 people, including five hijackers, 59 others aboard the plane, and 125 working in the building.
The impact of the plane severely damaged the structure of the building and caused its partial collapse. At the time of the attacks, the Pentagon was under renovation and several offices were unoccupied, resulting in fewer casualties. Only 800 of 4,500 people who would have been in the area were there because of the work.
When the damaged section of the Pentagon was rebuilt, a small indoor memorial and chapel were included, located at the point of impact. For the fifth anniversary of the September 11, 2001 attacks, a memorial of 184 beams of light shone up from the center courtyard of the Pentagon, one light for each victim of the attack
For newcomers to the Washington area, the first problem encountered is getting around. The Pentagon is actually located in Arlington, Virginia, across the Potomac River from Washington, DC, and at the convergence of several major roadways. Careful planning and attention to directional signs is a must for the newcomer. Generally, approach to the Pentagon will be on the Henry G. Shirley Memorial Highway .
Visitor should park only in designated parking areas. Parking in other than the visitors lots is reserved for parking permits and is strictly enforced. In the assignment of spaces, preference is given to carpools, although some parking permits are available for unusual working hours or special situations.
The only way to enter the Pentagon building is by escort or building pass. An Armed Forces identification card can be used on week days during normal duty hours only. Visitors without a building pass are screened by electronic detectors.