Just last month, the owners of Chicago's iconic Willis Tower released plans to upgrade the landmark facility with new retail and dining destinations and an enhanced observation deck. Now, Blackstone Group has unveiled some additional thrilling details of the project, including a potential rappelling feature that would allow visitors to descend from the 103rd to 102nd floor inside a glass box. 

Improvements to the Willis Tower could include a rappelling attraction and exterior staircase, image via Crain's

And that's just the beginning. Another glass enclosure, dubbed the "Ledgewalk," would put visitors in a stepped transparent shelter wrapping around one of the building's corners. Positioned more than 1,300 feet from the ground, the ledge would be open-air and exposed to the elements, but participants would be attached to a safety harness. The improvements to the skyscraper's famous Skydeck, which already includes protruding glass boxes called 'The Ledge,' would cost $20 million and would double the current capacity of 600 visitors.

An enhanced base and retail podium are planned, image via Blackstone Group

The $546 million renovation project would include a new three-storey retail and entertainment pavilion at the base of the 108-storey tower. The introduction of an enormous food hall is designed as an enticing olive branch to companies looking for high-profile office space in the core. And Blackstone's 2016 figures indicate that operating income at the Skydeck sharply increased 22 percent to $30 million from 2014.

Renovations include retail and entertainment facilities, image via Blackstone Group

The attraction currently draws about 1.7 million customers every year. The enhancements will help the Willis Tower compete with another observation deck at the John Hancock Center, which features a similar vertigo-inducing attraction that tilts sectioned pods of the observatory outwards.

Willis Tower, image by Marcus Mitanis

Additional images and information can be found in the Database file linked below. Want to get involved in the discussion or share your photos? Check out the associated Forum thread or leave a comment at the bottom of this page.