Nancy Holt made drawings for several large-scale public art projects that remain unrealized and exist only as proposals. In 1984 she developed O Silo for an experimental project at Bard College—Land Marks: New Site Proposals by Twenty-Two Original Pioneers of Environmental Art—where artists were asked to develop an artwork for a site on the college’s campus. The artists received plans, photographs, topographical maps, details of underground cables, and information on weather conditions. They were given no restrictions on finances or logistics by the curator, Linda Weintraub. All twenty-two projects remain unrealized.

Holt’s proposal for O Silo is seen here in drawings and in a photograph of the model in its packing crate. She proposed a series of architectural structures with apertures aligned with the sunrise and sunset at the solstices and equinoxes, the tallest standing at 90 ft. (27.4 m). From a viewing platform at the top, one would be able to see the Hudson River, which at ground level is obscured by trees. Standing within the sculpture and looking up through each structure, one would see a circle of sky, while looking down would reveal a circle of ground, interrupted by a changing circle of light. O Silo shows Holt’s interest in the circle and in the constantly shifting qualities of light.