Noted "earthworks" artist Walter De Maria's 1977 avant-garde installation consists of 140 tons of gently sculpted soil (22 inches deep). It fills 3,600 square feet of a second-floor gallery maintained by the Dia Art Foundation since 1980. As the New York Times put it in 1999, "a loamy smell definitely permeates the space." You can't touch or walk on the dirt, nor can you take its photo. If you like this installation, check out De Maria's equally odd and impressive work, The Broken Kilometer, an 18.75-ton installation that consists of five columns of a total of 1,000 meter-long brass rods, which cover the wood floors of an open loft space. It's a few blocks away at 393 West Broadway, and has the same hours as the Earth Room.