 The two had previously worked together closely on the design of cantonments.Somervell gave them until 9am on Monday morning to design the building, which he envisaged as a modern, four-story structure with no elevators on the site of the old Washington Hoover Airport.Over that "very busy weekend", Casey, Bergstrom and their staff roughed out the design for a four-story, five-sided structure with a floor area of —twice that of the Empire State Building.