Archaeological sites may be excavated clandestinely to obtain objects and relics for sale on the art market or to museums. Such looting of sites destroys their value as a source of information on the cultures that lived there and on the origins of the modern culture in the region. It may also destroy the importance or beauty of sites for visitors, whether foreigners or citizens of the country.
Recently clandestine or illicit excavations have increased considerably and in some cases are conducted on a large scale with advanced equipment. The Four Corners area in the southwest of the USA as estimated 60-95% of some 1.5 million sites including cliff dwellings, dry caves and buried villages have been looted. Under-water thieving of historical objects has grown to considerable proportions as well.