query: Where is the worlds tallest building?
passage: List of tallest buildings and structures
The world's tallest artificial structure is the 829.8-metre-tall (2,722ft) Burj Khalifa in Dubai (of the United Arab Emirates). The building gained the official title of "Tallest Building in the World" and the tallest self-supported structure at its opening on January 9, 2010. The second-tallest self-supporting structure and the tallest tower is the Tokyo Skytree. The tallest guyed structure is the KVLY-TV mast.
passage: Culture of Chicago
The tallest buildings in Chicago are Willis Tower, Trump Tower, the Aon Center, 875 North Michigan Avenue, and the Franklin Center. Willis Tower was originally named Sears Tower, and was the tallest building in the world from 1973 to 1998. It is now the second-tallest building in the United States, after One World Trade Center, though the height to the roof of Willis Tower is greater than that of One World Trade Center.