About 176,000 years ago, Neanderthals built enormous rings from broken stone formations 336 meters inside a French cave — more than two tonnes of material arranged in total darkness for a purpose archaeologists still cannot explain - Space Daily

Two and a bit tonnes of snapped rock, stacked into neat circles, in a chamber that has never once seen daylight. Nobody has worked out why. Bruniquel Cave sits above the Aveyron gorges in the Tarn-…