A look inside the Pentagon, the heart of the US military

Located in Arlington, Virginia, just across the Potomac River from Washington, D.C., the Pentagon has served as the epicenter of the U.S. military, housing the Department of Defense, the Army, the Navy, and the Air Force, since the 1940s.  (Photo By Bill Clark/CQ-Roll Call, Inc via Getty Images)

What was once a Virginia neighborhood known as Hell’s Bottom was cleared out and torn down to make way for the 150-acre Pentagon, with construction beginning on Sept. 11, 1941. The facility was completed and dedicated in 1943. The Pentagon was commissioned after Henry L. Stimson, Secretary of War to President Franklin D. Roosevelt, noted that the Department of War (now the Department of Defense) was unable to function effectively in its old headquarters, the Munitions Building in Washington, D.C., due to a lack of space.   (Photo by Smith Collection/Gado/Getty Images)

Constructed during World War II, usage of steel in the Pentagon’s construction was instructed to be kept at a minimum due to supply chain issues, and the building was to be limited to a maximum height of about 77 feet to preserve the view from Washington of Arlington National Cemetery. President Franklin D. Roosevelt also suggested that the Pentagon have no windows to better protect it from air raids, though the current design, proposed by George Edwin Bergstrom, was eventually the one FDR chose to adopt.  (Photo by Win McNamee/Getty Images)

The Pentagon’s corridors are comprised of five concentric rings, each connected by hallways heading inward toward its large courtyard. The massive building was also constructed when segregation was still commonplace in the South, and therefore was designed to comply with Virginia’s Jim Crow laws with separate eating and lavatory facilities for white and black employees. This changed under FDR’s direction, despite protests by the state government, making the Pentagon the first desegregated building in Virginia. Until 2011 – when a 17-year-long renovation project was completed – the Pentagon only had one elevator, which was reserved for the Secretary of Defense. This renovation also closed off the wing of the Pentagon struck on 9/11, potentially saving hundreds of employees who would otherwise have been working in the impact zone. (Rich Clement/Bloomberg via Getty Images)

The Pentagon, as the headquarters of the U.S. Department of Defense, also serves as a primary headquarters for the Army, Navy, and Air Force. The Pentagon is mainly used for bureaucratic operations, with about half of its floor space being occupied by offices. Nearly 30,000 civilian and military personnel work in the Pentagon, which is the world’s largest office building. The Pentagon also contains multiple chain stores and amenities, such as a food court, a federal credit union, a CVS pharmacy, a Starbucks, and a Subway restaurant.  (Rich Clement/Bloomberg via Getty Images)

The Pentagon’s Hall of Heroes, first opened in 1968, is a space used to commemorate about 3,500 Medal of Honor recipients in the Army, Sea Service, and the Air Force. Located on the second floor on the Pentagon’s main concourse, the Hall of Heroes is also used as a primary hosting venue for events, which include speeches, promotions, retirements, and other ceremonies.  (Photo by Cheriss May/NurPhoto via Getty Images)

At 9:37 a.m. on Sept. 11, 2001, American Airlines Flight 77, hijacked by al Qaeda terrorists while en route to Los Angeles from Virginia’s Dulles International Airport, struck the Pentagon’s west wing, killing 125 people – 55 military personnel and 70 civilians – inside, and caused part of the west wing to collapse. Restoration of the west wing was completed in 2002, and an outdoor memorial was completed and opened in 2008. The memorial features an arrangement of 184 benches directly in front of the section of the Pentagon that Flight 77 hit, each dedicated to an individual victim aboard the plane or inside the building that died in the attack.  (Photo by Alex Wong/Getty Images)

The Pentagon resumed operations shortly after post-9/11 repairs were completed, and continues employing tens of thousands of military personnel and bureaucrats. The building is also open to the public for regular tours, occurring each Tuesday and Thursday at 10 a.m. and 1 p.m. However, Pentagon tours are highly restrictive, with only pre-approved U.S. citizens being allowed in after planning well in advance. Pentagon tours were temporarily suspended during the recent COVID-19 pandemic.  (Photo by SAUL LOEB/AFP via Getty Images)