With 44,000 U.S. tons (40,000 metric tons) of structural steel, and almost one full acre per floor, this 64-story office building is the one of the largest privately owned buildings in the world. The exterior wall is of unconventional construction, with floors attached to the exterior column at every third story.... the primary structure, then, is on a 3-story module. There is no "architectural" cladding of the columns, as the weathering steel of the structure is left exposed to the elements. This corporate headquarters includes retail and restaurant space, parking for 600 cars and features a rooftop heliport.