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
The Gogo Building district along the Chicago River. There are two large red brick buildings along the Chicago River just south of where the river splits, formerly known as the Butler Brothers Warehouse buildings. They were both designed for the Butler Brothers Company, a mail order company, similar to Montgomery Ward's and Sears & Roebuck at the time. The northern structure was designed by Daniel Burnham, a famous Chicago architect, with its completion date being 1913, a year after Burnham’s death. This building only stood for 7 years before being completely demolished and rebuilt exactly as it stood before by the Chicago Union