Willis Tower

Willis Tower — long known as the Sears Tower — rises 1,451 feet (442 m) over Chicago and was the tallest building in the world from its completion in 1973 until 1998. Its bundled-tube structural design, a cluster of nine square tubes rising to different heights, was a landmark of engineering. Its glass Skydeck ledges, jutting out from the 103rd floor, let visitors stand over the city on a transparent floor.

• Chicago
  The third-largest U.S. city, on Lake Michigan related