The Willis Tower Skydeck is one of Chicago's most popular tourist attractions, but Blackstone Group believes its true potential has yet to be tapped. A sizable amount of Blackstone and Equity Office's $500M renovations to Chicago's tallest building are earmarked for the Skydeck. Crain's Chicago Business (citing Morningstar Credit Ratings) reports those renovations could radically alter Willis' top floors.

The possible additions to the Skydeck include a glass-enclosed rappel line from the 103rd floor to the 102nd floor, and an outdoor glass ledge where visitors, clipped to safety harnesses, can walk around and take in the views. Blackstone plans to spend $20M renovating the Skydeck and observatory. These plans fall in line with the "thrill attraction" options Equity Office director of development Paul Kurzawa told Bisnow last month that Blackstone was exploring as part of the tower's repositioning.

Skydeck and observatory revenue reached $29.9M last year, a 22% increase from 2014. Adding thrill attractions like rapelling and a ledgewalk would be a welcome addition to the Skydeck's operating income and popularity with tourists. There is precedent for skyscraper thrill attractions in Chicago. John Hancock Center, which rebranded its observatory as 360 Chicago, added TILT!, a feature where visitors enter a glass structure that leans outside of the observatory, giving them views of Michigan Avenue 1,000 feet below. Another popular supertall thrill attraction is the Edgewalk at Toronto's CN Tower, where visitors strap themselves into safety harnesses and walk on a ledge outside the tower's main observatory, 1,100 feet above downtown Toronto.