Blackstone buying Chicago's Willis Tower, once known as Sears Tower, for undisclosed amount

Blackstone is buying Chicago's Willis Tower, once called the Sears Tower, from 233 South Wacker LLC for an undisclosed amount.

The Willis Tower is 110-stories and the second-tallest office building in the U.S. It is the fifth-tallest office building in the world.

The Willis Tower's Skydeck, located on the 103rd floor, is a popular tourist attraction. It provides 1.6 million visitors a year with views of Chicago and the surrounding area including from the "Ledge," glass cubes which extend from the building.

Jacob Werner, a managing director in Blackstone's real estate group, said in a statement on Monday that Blackstone sees "great potential in further improving both the building's retail operations and the tourist experience for one of the most popular destinations for visitors to Chicago."