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
Chicago Water Tower Pumping Station, it drew clean water from water cribs in Lake Michigan. The tower gained prominence after the Great Chicago Fire of 1871. While some incorrectly believe that the tower was the only building to survive the fire, a few other buildings in the burned district survived along with the tower. The tower was the only public building in the burned zone to survive, and is one of just a few of the surviving structures still standing. In the years since the fire, the tower has become a symbol of old Chicago and of the city's recovery from the fire.