Four teenagers discovered the Lascaux cave in France in September 1940, after their dog, Robot, led them to a hole in the ground. Inside, they found remarkable prehistoric artwork, including hundreds of paintings and thousands of engravings dating to the Upper Paleolithic period. Lascaux was later closed to visitors after large crowds caused changes to the caves delicate environment, threatening the artwork. Today, replicas allow visitors to experience the ancient artistic treasure while helping protect the original paintings.