Robert Smithson's monumental earthwork Spiral Jetty (1970) is located on the Great Salt Lake. The artist used black basalt rocks and earth from the site to create a coil 1500 feet long and 15 feet wide that extends out counterclockwise into the changing pink, red, blue, or cloudy white water.

For more information click on the following links:
http://www.spiraljetty.org 
http://ludb.clui.org/ex/i/UT3127/
http://en.wikipedia.org/wiki/Spiral_Jetty
http://www.sculpture.org/documents/scmag04/julaug04/spiraljetty/julaug04_spiraljetty.shtml

For more information, images and films on Robert Smithson and his work
http://www.robertsmithson.com/earthworks/spiral_jetty.htm