Robert Smithson created Spiral Jetty.
Spiral Jetty is a large earthwork built in 1970 on the northeastern shore of Utah’s Great Salt Lake. Smithson constructed the spiral from local basalt rocks, earth, and salt crystals, extending it into the lake as a monumental example of Land art.
Its appearance changes with the lake’s water level. At times it is clearly visible as a dark spiral; at other times much of it is submerged. This changing condition is central to the work’s meaning and physical experience.
The work is associated with the Dia Art Foundation rather than being a signature object of the Solomon R. Guggenheim Museum. It has nevertheless been exhibited in major museum contexts, and the question’s wording distinguishes the artist and title from Guggenheim-specific collection objects.