The Pentagon is the headquarters of the United States Department of Defense, located in Arlington, Virginia. It is a large, five-sided building that serves as a central hub for military planning and operations. Constructed during World War II, it is one of the largest office buildings in the world, housing approximately 23,000 military and civilian employees. The design of the Pentagon features five sides, five floors, and a unique layout that allows for efficient movement within the building. It is also known for its iconic status and has become a symbol of American military power and national security.