This 110-storey building, a real feat of engineering, was called the Sears Tower until 2009. Nowadays it is the second tallest skyscraper in the US and the fifth tallest in the world. The tower is composed of nine rectangles resting on more than 100 steel and concrete caissons anchored into the bedrock dozens of metres below ground. The Skydeck on the 102nd floor offers a unique view for visitors. The entrance on Wacker Drive is dominated by an artwork by Alexander Calder, entitled The Universe.