The Willis Tower, built as and still commonly referred to as the Sears Tower, is a 110-story, 1,450-foot skyscraper in Chicago, Illinois.  At completion in 1973, it surpassed the World Trade Center in New York to become the tallest building in the world, a title it held for nearly 25 years; it now stands as the 2nd tallest building in the Western Hemisphere and 16th-tallest in the world. Willis Tower was the first building to use this innovative "bundled tube" structure design and is now undgoing rennovations to expand its footprint. 

As part of the transformation, more than 300,000 square feet of new retail, dining and entertainment space, called the Catalog, to be added to the base of the building. The Catalog will fill up five stories of the redevelopment and will be topped by a new 30,000-square-foot outdoor deck and garden space.