Lascaux cave paintings. Discovered in 1940 by four teenagers. By 1955, the carbon dioxide produced by 1,200 visitors per day had visibly damaged the paintings. The cave was closed to the public in 1963 in order to preserve the art.
Chauvet Cave paintings discovered 1994 Paleolithic 40,000-10,000 BCE Google Image Result for http://2.bp.blogspot.com/-Vk5mK4qKV6w/TdsLPLkuYYI/AAAAAAAABFY/ejmM_oXBxZc/s640/634x375chauvet-cave-rhino-painting_2351.jpg
Tassili n'Ajjer (Plateau of the Rivers) is a vast plateau in south-east Algeria at the borders of Libya and Niger. The range is noted for its prehistoric rock art and other ancient archaeological sites, dating from the Neolithic era when the local climate was less dry, savannah rather than desert. The art is no older than 9–10 millennia, but may be younger.