Architecture of Chicago a new structural system of framed tubes in skyscraper design and construction. The first building to apply the tube-frame construction was the DeWitt-Chestnut Apartment Building which Khan designed and was completed in Chicago by 1966. This laid the foundations for the tube structures of many other later skyscrapers, including his own constructions of the John Hancock Center and Willis Tower (then named the Sears Tower) in Chicago and can be seen in the construction of the World Trade Center, Petronas Towers, Jin Mao Building, and most other supertall skyscrapers since the 1960s. Willis Tower would be the world's tallest building
Sears, Roebuck and Company Complex a modillioned cornice. It housed water tanks for firefighting on the upper levels, as well as offices and secretarial training facilities. It also housed the early broadcast facilities for WLS-AM. In 2015, it was refurbished and reopened to the public as the "John D. and Alexandra C. Nichols Tower". It now houses non-profit groups and offices, including a classroom on the 12th floor for the School of the Art Institute of Chicago. The Sears Roebuck plaque is still visible on top of the building. The Sears, Roebuck and Company Administration Building is a broad five-story masonry building, occupying about 3/4