Piecing together prehistoric human development from a time before written language is tough work,  usually reliant on interpreting artifacts. The finding of such artifacts is rare enough; finding them in whole, unspoiled conditions is even rarer. But to find a series of such artifacts, almost completely untouched by the elements or human or animal interference – as happened near Montignac, France – was nothing less than revolutionary.

On this day, September 12, in 1940, several teenagers playing on the hill went down into a hole in the ground left by an uprooted pine tree. What they found was an enormous grotto, 66 feet long by 16 feet wide, with depictions of horses, red deer, stags, bovines, felines and assorted mythical creatures, drawn in excellent detail and with striking colors.

The cave is presumed to have been the center of prehistoric hunting ceremonies, and the animals drawn on its walls are featured without any kind of background — no vegetation, no humans (except for one human-like form). Scientists have estimated the drawings were made an amazing 17,000 years ago – some of the earliest human art ever discovered. Due to the enormous tourist traffic the cave generated, the government closed down the site to all but a few scientists, and opened a replica cave nearby. Many of the drawings were also put up on the Lascaux caves website.