CHICAGO, IL - OCT 1: Willis tower close up on October 1, 2011 in Chicago, Illinois. Willis Tower know as the famous landmark is 1451 feet high as the world's tallest for 25 years since its completion.
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CHICAGO, IL - OCT 1: Willis tower close up on October 1, 2011 in Chicago, Illinois. Willis Tower know as the famous landmark is 1451 feet high as the world's tallest for 25 years since its completion.