Spiral Jetty, Utah

Spiral Jetty is a basalt spiral 1500 feet long and 15 feet wide, which protrudes from the shore of the Great Salt Lake, on submerged land leased from the state. It was built by the artist Robert Smithson in 1970. For much of its existence, Spiral Jetty was invisible, lying a few feet under the fluctuating surface level of the lake. Its stones started poking out of the water around 1994, and by 2004 drier regional conditions had lowered the lake enough to expose the Jetty, during a period that conveniently corresponded with a major traveling retrospective of the artist's work. It has been high and dry since then, and is now frequently visited.  Dia Art Foundation of New York acquired the piece from Smithson's estate in 1999.