Take a tour of Willis Tower in Chicago, United States – part of the World’s Greatest Attractions series by GeoBeats. For 25 years, it was the world's tallest building. The sky-scraping Willis Tower is Chicago's pride and joy, drawing millions of visitors. The roof of the tower tops out at 1,450 feet, with antenna towers reaching 1,730 feet. From its skydeck, you have the ability to see 4 states. The Skydeck also features glass boxes which look 1,353 feet down to the street below. Previously known as the Sears Tower, it is one of Chicago's biggest attractions.