176,500 years ago, long before modern humans left Africa for the Eurasian continent, a band of Neanderthals conducted an elaborate ritual deep inside Bruniquel Cave in a region we know today as southern France. The Neanderthal group wrested hundreds of stalagmites from the floor of the cave to build elaborate circular structures, their work illuminated only by firelight. Discovered by archaeologists in the 1990s, the cave system is so large that many of its great treasures are hidden far from its entrance, which suggests it was thoroughly explored and probably inhabited for some period of time. This new part of the cave, analyzed only recently, adds to our understanding of Neanderthal social life.

The Neanderthal structure was mostly undisturbed for tens of thousands of years with the exception of a few hibernating bears. Recounting their discovery in Nature, a group of archaeologists say there is no question that the structures were created deliberately by humans, especially because there is evidence that the stalagmites were wrenched from the cave floor and stacked in circular patterns. Burn marks on the roughly 400 stones show that fires were built inside the structure, and one area contains burned bones. The bones could mean that this was a feasting place, but its difficult-to-reach location and the nature of the design suggest a more symbolic use. Based on the burn patterns, it seems that the structures themselves were designed to light on fire, creating what would have appeared to be circles of flaming stone in the otherwise pitch-black cave.