II.

The Original Twin Towers

The World Trade Center occupied a 6.5-hectare (16-acre) site and contained about 836,000 sq m (9 million sq ft) of office space in the twin towers. Four smaller buildings and a 47-story high-rise occupied a plaza surrounding the towers and housed shops, exhibition pavilions, and additional offices. The complex numbered more than 430 businesses and government agencies among its tenants, including the investment firm Morgan Stanley, the Bank of America, and the Port Authority of New York and New Jersey, the agency that owned and operated the World Trade Center. About 50,000 people worked in the complex, and another 80,000 visited it daily. Subways transported people to and from a station underneath the complex. A concourse of shops was also located underground.

The modern steel-and-glass towers that Yamasaki created for the World Trade Center had a light and airy feeling. Columns of thin steel tubing sheathed the exterior and provided substantial support for the weight of the towers. The tubes were placed 56 cm (22 in) apart, and narrow windows filled the space in between. The close spacing of the tubes made the building appear from a distance to have a solid exterior of gleaming metal. At plaza level the exterior tubing formed graceful arches that reminded many critics of Gothic architecture. The decorative arches and exterior tubing drew criticism for their departure from the austere aesthetic of modernism. The fact that the walls were load-bearing also struck critics as a retreat from the nonload-bearing “curtain wall” construction typical of most modern skyscrapers.

The towers had square floor plans; no internal supports broke up the interior space between the outer walls and the central core, which housed elevators, stairwells, and other facilities. This plan provided the towers with an enormous amount of rentable floor space, about an acre per floor. Each tower had 104 elevators. From an observation deck on the 107th floor of Tower Two, visitors could see for 72 km (45 mi) in four directions. A restaurant, Windows on the World, topped Tower One.