Chicago Willis Tower

list of tallest buildings in the world http://en.wikipedia.org/wiki/List_of_tallest_buildings_and_structures_in_the_world
http://en.wikipedia.org/wiki/List_of_tallest_buildings_in_the_world
http://en.wikipedia.org/wiki/Skyscraper
http://en.wikipedia.org/wiki/History_of_the_tallest_buildings_in_the_world