Largest administrative building

The largest office building is the Pentagon, in Arlington, Virginia, USA, which has a floor area of 604,000 m² (6.5 million ft²). Each of the outermost sides is 281 m (921 ft) long and the perimeter of the building is about 1,405 m (4,610 ft). Its corridors total 28 km (17.5 miles) in length, and there are 7,754 windows to be cleaned. There are over 26,000 military and civilian employees working in the building. The building was completed on 15 January 1943 and cost an estimated $83 million (£20.5 million at 1943 rates).