For years, up to 1,500 people a day filed past the 17,000-year-old paintings at Lascaux in France, until the carbon dioxide in their breath started growing crystals and lichen on the walls — so the government sealed the cave in 1963 and later built visitors an exact replica a couple of hundred meters away

In September 1940, four teenagers and a dog stumbled into a hole in a hillside near Montignac, in southwestern France, and found themselves standing inside a painted Ice Age cathedral. The walls of the Lascaux cave were covered in bulls, horses, stags and abstract signs — some 600 paintings and nearly 1,500 engravings, laid down [...] The post For years, up to 1,500 people a day filed past the 17,000-year-old paintings at Lascaux in France, until the carbon dioxide in their breath started growin