Burj Khalifa with Smith's attempts to make the crown more slender. The building opened on 4 January 2010. The tower was designed by Skidmore, Owings and Merrill (SOM), which also designed the Willis Tower (formerly the Sears Tower) in Chicago and the One World Trade Center in New York City. Burj Khalifa uses the bundled tube design of the Willis Tower, invented by Fazlur Rahman Khan. Due to its tubular system, proportionally only half the amount of steel was used in the construction, compared to the Empire State Building. Khan's contributions to the design of tall buildings have had a profound impact
Century Tower (Chicago) is listed in the National Register of Historic Places. This building has formerly been named: Century Tower (Chicago) The Century Tower Condominiums, formerly known as the Trustees System Service Building, is a historic building located at 182 West Lake Street in the Loop in Chicago, Illinois. The building was designed in 1929 and completed in 1930; at the time of its completion, it was the tallest reinforced concrete building in the world. Its original tenant and namesake was the Trustees Service System, a bank that specialized in consumer loans. Architects Thielbar and Fugard designed the building in the Art Deco