The Blackstone Group didn't pay a record $1.3B for Willis Tower two years ago just to sit back and leave Chicago's tallest building alone. Yesterday, Blackstone and Equity Office unveiled plans for a $500M renovation project they say will finally release the untapped potential of the 4.6M SF skyscraper.

Blackstone Group global head of real estate Jon Gray (at the podium) said this is the largest single investment in a Blackstone asset in the company's history, and Emanuel called it "a half-billion-dollar commitment to Chicago." Blackstone is receiving no tax breaks or contributions from the city.

Gray said the renovations will "restore and transform an iconic American skyscraper." The improvements will "reconnect it to the neighborhood" and make Willis a true place to work, play and explore for office tenants, local visitors and tourists. Blackstone will reconfigure 460k SF within the building. Approximately 150k SF will be for exclusive tenant use, including a full-service fitness center, tenant lounges, private workspace and concierge services.

The man in charge of executing the renovations is Equity Office managing director of development Paul Kurzawa, who joined the firm last March from Dreamworks Animation. Kurzawa studied Bruce Graham's and Fazlur Rahman Khan's original blueprints to determine where Willis Tower fits in with the flurry of development activity surrounding it. "Right now, a worker in Willis needs to walk three or four blocks in order to find a good lounge, a restaurant or a fitness center," he said. "We want to create a neighborhood here that doesn't exist right now."

Fitting, given his experience with Dreamworks, Kurzawa said Equity Office is in talks with a major media company to bring a thrill attraction to Willis Tower's observatory that will convincingly convey what it feels like to be more than 1,300 feet above street level.

When the improvements are complete, people visiting Willis Tower will enter the building through a three-story glass podium. This will connect to a completely rehabbed office lobby and 300k SF of new retail, dining and entertainment options. Kurzawa said Equity Office is already in advanced negotiations with prospective tenants for half of that footprint.

Here is a rendering of Willis Tower's future glass-enclosed winter garden, which will provide visitors and tenants with unfettered views of the 110 stories above.

One of the highlights of the renovations will be an outdoor rooftop deck. Gray said this will be accessible to visitors all year long and will include a skating rink during the winter months.

Equity Office president/CEO Eli Khouri said the renovations will merge Graham's original vision for Willis with the changing needs of modern life. Graham said one of the the main factors influencing Willis' location is its accessibility to all forms of public transportation, and its proximity to Chicago's civic and cultural institutions. "It is a tower of the people," Khouri said. The trends that Blackstone and Equity will draw from are being driven by Millennials, but Khouri said they cross generations. Equity will move its offices to Willis in 2018.

Blackstone and Equity are also giving back to the community. Gray announced a $100k donation to Project Pipeline, a program sponsored by the Illinois Chapter of the National Association of Minority Architects. The contribution will allow Project Pipeline to double the number of students served by its architectural summer camp, increase scholarship funding for the program, and set up an eight-week design-build program for high school students who will work to renovate a community space in the city. Equity Office will also donate 5,000 Skydeck tickets annually to Chicago Public Schools students.