Constructed in the 1970s, the Spiral Jetty project by Robert Smithson is a cornerstone work in the realm of American land and water art. This coiled monument snakes into the water with a length of 1500 feet and more than wide enough for two vehicles to pass along it. Perhaps the most interesting aspect of this project is that it was entirely submerged due to rising water levels shortly after being created and remained underwater for decades. It was only as recently as 2004 that it resurfaced during drought conditions matching those during the time of its original creation – remarkably intact though with a changed color reflecting the accretion of salt. (Source)