The structures found inside Bruniquel cave in France. (Credit: Etienne FABRE/SSAC) Circular structures discovered in a French cave continue to build the case that Neanderthals were more intelligent than we give them credit for. Deep inside the Bruniquel Cave, researchers discovered two rings of stalactites and stalagmites that appeared to have been deliberately stacked and arranged to form a structure. The site also contained charred animal bones, which may have served as torches to illuminate the dark depths of the cave or keep bears at bay. The thing is, a new dating analysis suggests these structures were built more than 170,000 years ago, long before Homo sapiens arrived in the area. That means Neanderthals were the likely architects, and we didn't expect them to be such adept builders and cave explorers.