The creator of some of the most significant Earthworks of the Land Art movement, Nancy Holt’s exterior installations and public sculpture exist in dialogue with the elements and perceptions of time and space. Her Sun Tunnels (1973–6) consists of huge concrete tunnels built on 40 acres in Utah whose positions are aligned with the sunrises and sunsets of the solstices in order to channel the intensity of desert light. Hydra’s Head (1974) is an arrangement of concrete cylinders on a riverbank that correspond to the constellation above. She documented these large-scale poetic forms, which take art out of the museum and into the natural landscape, in film and photography. Married to Robert Smithson, she petitioned against drilling near the site of his Spiral Jetty (a giant spiral of black basalt rock) in 2008.