Plans have been revealed for a $500 million renovation of Chicago’s iconic Willis Tower. The renovation will be the first since the 108-story tower was completed 43 years ago. Gensler’s Chicago office is leading the design for the project, which is being initiated by Blackstone and Equity Office.

The plan for the Willis Tower includes the transformation of approximately 460,000 square feet of the building’s interior and a completely new public experience at its base. New amenities to the tower will include a fitness center, tenant lounges, and private event space. The tower’s observation floor, Skydeck Chicago on the 103rd story, will also be remodeled.

The base will include more than 300,000 square feet of new retail, dining, and entertainment spaces, and 30,000-square-foot outdoor deck and garden space. Included in the base’s redevelopment is a three-story glass structure atop the building’s plinth, as well as a three-story subterranean winter garden.

From the new subterranean winter garden, visitors will be able to look up 111 stories. (Blackstone and Equity Office)

From the new subterranean winter garden, visitors will be able to look up 111 stories. (Blackstone and Equity Office)

“With this historic investment the Willis Tower will remain a vibrant and modern icon that inspires both young and old for generations to come,” Chicago Mayor Rahm Emanuel said during the announcement of the renovation. “But more than that—today Blackstone is doubling-down on its confidence in the future we are building in the city of Chicago.”

Built in 1973, the Willis Tower was the tallest building in the world for nearly 25 years. It is still the second tallest in the United States, behind New York’s One World Trade Center. To achieve its immense height, architect Bruce Graham and engineer Fazlur Rahman Khan envisioned the building as nine square structural tubes.

As part of the renovation announcement, Equity Office committed to offering 5,000 Skydeck tickets to Chicago Public School students. Equity Office will also donate $100,000 to Project Pipeline, a program sponsored by the Illinois chapter of the National Association of Minority Architects (I-NOMA). Project Pipeline’s goal is to educate and mentor minority students through the process of becoming licensed architects.

The tower was renamed the Willis Tower in 2009. Many Chicagoans still refer to the building by its original name, the Sears Tower.

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