"The Pentagon it's the world's largest low-rise office building. The entire U.S. Capitol building could fit inside any of the building's five wedges," the The Department of Defense says.

"It has 6,500,000 square feet of office space (three times the floor space in the Empire State Building!), 7,754 windows and 17 1/2 miles of corridors. Yet, its spoke-and-ring design means it takes only about 7 minutes to walk between the furthest two points in the building.

"During construction, the builders were able to conserve enough steel to build a battleship. And the 689,000 tons of sand and gravel used to make the building's reinforced concrete – including 41,000 concrete pilings – came from the nearby Potomac River."

"A 17-year-long renovation project that finished in 2011 saw 70 passenger elevators installed in the building. Until then, people who couldn't use stairs used long ramps to move between floors," the defense.gov says.

"The Pentagon is divided into five wedges, and the renovation project was going wedge by wedge when terrorists flew American Airlines Flight 77 into the Pentagon, Sept. 11, 2001, killing 189 people.

"The plane hit in Wedge 3, where renovations had just completed, but only about 800 out of the 4,500 people who normally would have been working there had moved back into their offices. And the new sprinkler system, extra structural support and blast-resistant windows helped to keep the building damage to a minimum, likely saving additional lives."

"More than 15,000 workers were on site around the clock, and wartime office space shortages meant that workers moved in before the Pentagon was fully finished," the defense.gov says.

"Construction finished on Jan. 15, 1943, just 16 months after it started. Speed costs money, though: Initially budgeted at $35 million, the final cost was $63 million, more than $900 million in today's money.

"Col. Leslie Groves, an Army Corps of Engineer officer, took charge of the Pentagon's construction in August 1941. He worked six days a week in his office in Washington. Then on Sundays, he would visit the project he felt most needed his personal attention."

"The Pentagon, one of the world's largest office buildings, is the headquarters of the Department of Defense. Located in the Washington, D.C., area, the five-sided building has three times the floor space of the Empire State Building.

"Each year, about 100,000 visitors explore displays and memorials in the Pentagon's halls with the help of tour guides, all of whom are active U.S. military service members.

"You must follow important details and security guidelines to reserve a Pentagon tour and be cleared to enter the Pentagon for your tour. Tours fill up quickly, and reservations are required at least 14 days in advance through this website.

"The Pentagon is the headquarters building of the United States Department of Defense, in Arlington County, Virginia, across the Potomac River from Washington, D.C. The building was constructed on an accelerated schedule during World War II. As a symbol of the U.S. military, the phrase The Pentagon is often used as a metonym for the Department of Defense and its leadership.

"The building was designed by American architect George Bergstrom and built by contractor John McShain. Ground was broken on 11 September 1941, and the building was dedicated on 15 January 1943. General Brehon Somervell provided the major impetus to gain Congressional approval for the project; Colonel Leslie Groves was responsible for overseeing the project for the U.S. Army Corps of Engineers, which supervised it.

"The Pentagon is the world's second-largest office building, with about 6.5 million square feet (600,000 m2) of floor space, 3.7 million square feet (340,000 m2) of which are used as offices. The Pentagon building spans 28.7 acres (116,000 m2), and includes an additional 5.1 acres (21,000 m2) as a central courtyard.

"It has five sides, five floors above ground, two basement levels, and five ring corridors per floor with a total of 17.5 mi (28.2 km) of corridors, with a central five-acre (2.0 ha) pentagonal plaza. About 23,000 military and civilian employees work in the Pentagon, as well as about 3,000 non-defense support personnel." (Wikipedia)

"Pentagon, large five-sided building in Arlington county, Virginia, near Washington, D.C., that serves as the headquarters of the U.S. Department of Defense, including all three military services—Army, Navy, and Air Force," the Britannica says.



"Constructed during 1941–43, the Pentagon was intended to consolidate the offices of the War Department, which had occupied 17 separate facilities throughout Washington.

"At its completion at a cost of $83 million in January 1943, the Pentagon was the world’s largest office building, covering 29 acres (12 hectares)—including a 5-acre (2-hectare) central court—and containing roughly 3,700,000 square feet (344,000 square metres) of usable floor space for approximately 25,000 people."

"The Pentagon is the headquarters of the U.S. Department of Defense and houses the offices of the secretary of defense, the Joint Chiefs of Staff and the secretaries of the military departments," the Live Science says.

"Too large to be situated in downtown Washington, D.C., the Pentagon lies across the Potomac River, in Arlington County, Va. With more than 6.5 million square feet (604,000 square meters), it boasts three times the floor space of the Empire State Building.

"More than 3.7 million square feet (344,000 square meters) is used for offices and there are 17.5 miles (28 kilometers) of hallways. About 23,000 civilians and military personnel are employed within the building."

"On Sept. 11, 2001, the nation's sense of security was shattered when terrorists hijacked commercial airplanes and flew them into New York City's World Trade Center, into a field in rural Pennsylvania, and into the nation's symbol of military might.

"American Airlines Flight 77 crashed into the west side of the Pentagon, penetrating three of its five rings and killing 184 people. Thankfully, several offices in that area weren't occupied because of the ongoing renovations," the defense.gov says.

"In fact, one of the sections had just finished getting upgrades that improved security features, including walls and windows with greater blast resistance. An initial analysis after the attacks suggested that helped to save a lot of lives."

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