September 12, 1940 was a momentous day in the recent history of Europe. What discovery was made by four teenagers on that day?

On September 12, 1940, the entrance to the Lascaux Cave was discovered by 18 year old Marcel Ravidat. Ravidat (died in 1995) returned to the scene with three friends, Jacques Marsal, Georges Agnel, and Simon Coencas, and entered the cave via a long shaft. The teenagers discovered that the cave walls were covered with depictions of animals.

Galleries that suggest continuity, context or simply represent a cavern were given names. Those include the Hall of the Bulls, the Passageway, the Shaft, the Nave, the Apse, and the Chamber of Felines.

The cave complex was opened to the public in 1948. By 1955, carbon dioxide, heat, humidity, and other contaminants produced by 1,200 visitors per day had visibly damaged the paintings. Pollutants, deteriorated fungi and lichen increasingly infested the walls. Consequently the cave was closed to the public in 1963, the paintings were restored to their original state and a monitoring system was introduced.

Lascaux II, an exact copy of the Great Hall of the Bulls and the Painted Gallery, opened in 1983 in the cave's vicinity, a compromise and attempt to present an impression of the paintings' scale and composition for the public without harming the originals. A full range of Lascaux's parietal art is presented a few kilometres from the site at the Centre of Prehistoric Art, Le Parc du Thot, where there are also live animals representing ice-age fauna.