Earthworks are usually large-scale sculptures installed in the natural landscape or composed of materials taken from a specific site. Inherent in this approach to making art is a break with the dependence of artists on conventional sites for viewing, selling or displaying art, such as museums and galleries. Earth artists often take their work away from the cities and create monumental works in remote places. The condition and lifespan of an earthwork are always dictated, to some degree, by nature. Many times only the artist has a chance to view the completed work before it is compromised by man or ravaged by nature. The element of impermanence is crucial to the concept of many pieces. Extensive documentation of Earthworks is common. Maps, videos, drawings, writings and photographs are often made by the artists and taken into the galleries for viewing. Sculptor Robert Smithson has taken materials, such as rocks and soil, from selected sites and presented them in galleries as secondary, or non-sites, connected to and dependent upon the original, non-gallery site. Relationships to historical architecture, such as Stonehenge, and monuments, such as burial mounds, are apparent in these works, as is an interest in ritual and the experience of man.