On September 12, 1940, four boys who were following a lost dog discovered the Cave of Lascaux and its magnificent paintings of bulls, horses, cows, and deer.

http://www.culture.gouv.fr:80/culture/arcnat/lascaux/en

The cave is now closed to visitors to protect against the damage that humans can inflict through breathing. The increased humidity has damaged the original paintings. The solution was to build an exact replica, Lascaux II, for tourists to visit. The original Lascaux is a cave in the limestone of southern France. Lascaux II was built in an adjacent rock quarry, but it is made of cement over wire, so it doesn't suffer from the erosion caused by a damp limestone environment like the original. Sure, the copies of the paintings are affected by all those humans who visit the replica and breathe (how dare they!), but these copies can be redone when they start to fade. The artists use the same tools as the originals: minerals, hands, fingers, and spitting. It took years to copy every rock and indentation in the original and then to paint it using original methods, but it is worth it to preserve a fabulous site.