The Pentagon

The world's largest office building by floor area/Modern Buildings

The Pentagon in Arlington, Virginia, is the headquarters of the United States Department of Defense and the world's largest office building by floor area. Built in just 16 months during World War II, each of its five sides is 281 meters long, and the building covers a total floor area of 116,000 square meters across five concentric rings and five floors. Despite its enormous size, no point in the building is more than a 7-minute walk from any other point, thanks to its pentagonal design. It has its own zip code, its own fire department, and roughly 23,000 workers who probably still get lost sometimes.