Four boys, a dog and a hole in the ground

Teenagers chasing a dog down a hole near Montignac found a cave whose walls had been painted seventeen thousand years earlier.

Lascaux was opened to visitors after the war, and the breath of a thousand people a day grew algae and crystals over the paint. It closed in 1963 and has stayed closed; what tourists see now is a replica built next door, which is the only reason the original still exists.