The World's Largest Office Building

The Pentagon in Arlington, Virginia is the largest office building in the world, with 17.5 miles of corridors, 6.5 million square feet of floor space, and approximately 23,000 employees. Despite its enormous size, it was designed to minimize walking distances, and you can walk between any two points in the building in under seven minutes. Construction began in September 1941 and was completed in just 16 months, an extraordinary feat for a building of its complexity. The building's design was partly shaped by a wartime concrete shortage that led engineers to limit each floor slab to a maximum of one foot in thickness.

Source: Wikipedia