Cadillac Ranch is a public art installation and sculpture in Amarillo, Texas, U.S. It was created in 1974 by Chip Lord, Hudson Marquez and Doug Michels, who were a part of the art group Ant Farm, and it consists of what were (when originally installed during 1974) either older running used or junk Cadillac automobiles, representing a number of evolutions of the car line (most notably the birth and death of the defining feature of mid twentieth century Cadillacs; the tailfins) from 1949 to 1963, half-buried nose-first in the ground, at an angle corresponding to that of the Great Pyramid of Giza in Egypt. Cadillac Ranch is visible from the highway, and though it is located on private land, visiting it (by driving along a frontage road and entering the pasture by walking through an unlocked gate) is tacitly encouraged. In addition, writing graffiti on or otherwise spray-painting the vehicles is now encouraged, and the vehicles, which have long since lost their original colors, are wildly decorated. (Text from Wikipedia.org)
The only thing that I found to be disappointing about visiting Cadillac Ranch is that some of the graffiti artists were slobs who left their empty spray paint cans strewn all over the ground. They were surely lighter to carry out (being empty of paint) than they were to carry in.