Art form, developed in the 20th century, that involves or encompasses the spectator.
The environmental sculptor can use any medium, from mud and stone to light and sound. Indoor environmental works often incorporate sculptural figures in detailed settings in gallery or museum spaces. Outdoor works in natural or urban settings include "earthworks" (large-scale alterations of the Earth's surface effected by earth-moving equipment) such as Robert Smithson's Spiral Jetty (1970), a rock-and-dirt spiral 1,500 feet long in the Great Salt Lake. The wrapped buildings of Christo are notable urban environmental works.