Robert Smithson was an American artist famous for his land art works. His most famous work was Spiral Jetty, a 1,500 foot long spiral shaped jetty extending into Utah's Great Salt Lake constructed from rocks, earth, salt and algae. Smithson developed the concepts of "sites" and "non-sites" where a site was an outdoor artwork and a non-site could be displayed indoors, such as photographs from the outdoor site alongside materials from that location. He was interested in entropy, maps and aerial photos as ways to document sites.