Willis Tower

Height: 1,451 feet (442 meters)

Location: Chicago, IL, U.S.A.

Architect: Skidmore, Owings and Merrill (SOM)

The Willis Tower, previously called (and still commonly known as) the Sears Tower, was the world's tallest building for 25 years prior to the completion of the Petronas Towers in Kuala Lumpur. The building includes extensive retail space, a broadcast platform, a conference center, a fitness facility, and corporate offices. The tower's famous Ledge, made of glass boxes, extends 4 feet from the skyscraper's side and allows for visitors to view Chicago through a transparent floor from the 103rd floor.