Sears Tower,
is a 110-story skyscraper in Chicago, Illinois, and the second tallest building in the United States. It was finished in 1973 and became the tallest building in the world, at 1,451 feet, a rank it held for 25 years. The structure has a unique "bundled tube" design, made by nine separate tubes, with only two of the tubes reaching to the top 108th floor.