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At 110 stories and 1,730 feet tall, the former Sears Tower, designed by Skidmore, Owings & Merrill in 1974, was the world's tallest building until 1996. It may have lost the title and even changed its name, but the Willis Tower's 103rd-floor Skydeck and the Ledge remain hard to beat. Suspended 4.3 feet out from the building, this glass box offers thrills along with views; on a clear day, a whopping four states, Illinois, Michigan, Wisconsin, and Indiana, are visible. Check the visibility ratings at the security desk before you decide to ride up and take in the view. Interactive exhibits bring to life Chicago's dreamers, schemers, architects, musicians, and sports stars. Computer kiosks in six languages help international travelers key into Chicago hot spots. Knee-High Chicago is a 4-foot-high exhibit with cutouts of Chicago sports and history at a child's eye level. Enter on Jackson Boulevard to take the ear-popping ride to the 103rd-floor observatory. Video monitors turn the 70-second elevator ride into a fun-filled, thrilling trip. Before you leave, don't miss the spiraling Calder mobile sculpture The Universe in the ground-floor lobby on the Wacker Drive side.