Skyscrapers: Chicago Spire

Designed like a giant screw by architect Santiago Calatrava (who also did Sweden's Turning Torso), the Chicago Spire is one of the tallest skyscrapers in the world currently under construction. To be 609 metres (or exactly 2000ft) high, the Chicago Spire is being built next to the Chicago River, near the edge of Lake Michigan. It is a residential project, with 1,193 self-contained units, spread out over its 150 floors.

The Chicago Spire started construction in 2007 and is expected to be completed in 2012. The tower will be over 150 metres taller than Chicago's next tallest, the Sears Tower, and will have a total of 81,470 sq metres of floor area.

Although primarily residential, there will also be some office space and room for a hotel in the tower. Each of the floors rotates about 2 degrees out from the one below it, resulting in a graceful screw shape. When built it will be easily the tallest residential tower in the world, overtaking Q1 and the Eureka Tower, both in Australia.