About 176,500 years ago, Neanderthals created a pair of stone rings far within a cave (located in France) from stalagmites cut to similar heights ranging up to 16-inches. Why? No one knows. However, the discovery — which was made back in 1990 — was recently the subject of a study that found the structures date back to a time when Neanderthals would have made them. This further underscores reshaped notions of how intelligent Neanderthals were, and reveals a big mystery surrounding a possible ritual site.