The Leed Gold Chicago Spire designed by Santiago Calatrava will be the tallest building in Chicago and second-tallest in the world when it is completed in 2010. A geothermal system will draw in river water to cool the building – as a building of this size is almost always in cooling mode even in the dead of winter due to the heat generated by people and mechanical systems. Each floor is rotated a few degrees relative to the previous to give every resident and office-dweller in the structure a unique view.