It is called the Skulptur Projekte, held every 10 years in Münster, Germany taking place now.
This international exhibition invites artists from all over the world to create new work specific for the event. Some pictures here.
It is running parallel with the Documenta12 in Kassel, from June 17 to September 30, 2007.

Thanks to Forever Redeemed who pointed me to this video:
http://www.laudontech.com/Downloads/MainSt_LasVegas.mpg