Sears Tower

Chicago is set to claim one of the world's largest retail spaces and America's tallest building as green. The city announced during last week's Greenbuild conference that both the Sears Tower and the Merchandise Mart are being retrofitted to meet LEED certification through Leadership in Energy and Environmental Design ratings of the U.S. Green Building Council.

Shown towering over the green roof of a LEED-certified high-rise nearby, the Sears Tower opened in 1973 as the world's tallest skyscraper. That and 4.2 million square feet of retail space in the Merchandise Mart are being retrofitted with energy efficiencies and other green features, with support from the Clinton Climate Initiative. The Merchandise Mart, built in 1930, achieved LEED Silver certification last week. Its owners are moving forward with plans to expand green features, including the addition of a green roof.

The "City of Broad Shoulders" is known for its outsized, cutting-edge architecture. The world's first skyscraper was built there 122 years ago. Local architecture heroes include Louis Sullivan and Daniel Burnham of the Chicago School of architecture. The organic designs of Frank Lloyd Wright's Prairie School style are celebrated as ahead of their time.

Caption text by Elsa Wenzel, CNET associate editor

Editor's note: This photo gallery misidentified the designer of the 111 South Wacker tower. It was designed by Goettsch Partners.