CHICAGO - JULY 16: Commuters walk past the former Sears Tower July 16, 2009 in Chicago, Illinois. The building was renamed the Willis Tower today, after London-based insurance broker Willis Group Holdings, a major tenant in the building. The building, once the tallest in the world, was opened in 1973 to house the offices of the then largest retailer in the world Sears, Roebuck & Co. (Photo by Scott Olson/Getty Images)
World's tallest buildings
One World Trade Center became the tallest building in the Western Hemisphere when a silver spire topping the building was installed on Friday, May 10. Here's a look at the world's tallest buildings.