Robert Smithson's monumental earthwork Spiral Jetty (1970) is located on the Great Salt Lake in Utah. Using black basalt rocks and earth from the site, the artist created a coil 1500 feet long and 15 feet wide that stretches out counterclockwise into the translucent red water (taken from spiral jetty.org).
If you live in Northern Utah it is your obligation to go see the Spiral Jetty. It was a somewhat long, bumpy drive but I think it was worth it. Bring along a picnic and make it an afternoon. Where else can you see earth art like this so close to home?
Here is a really interesting article to check out about it: http://query.nytimes.com/gst/fullpage.html?res=980DE0DF113BF930A25753C1A9649C8B63
Ginger and I at the center.