Bruniquel Cave is an archeological site near Bruniquel, France which contains cultural artifacts believed to have been created by Neanderthals. The artifacts are dated to 176.5 thousand years (±2.1 thousand years) ago. Two large rings formed from deliberately broken stalagmites, stacks of stalagmites, burned bear bones, and evidence of fire were found far underground, 336 meters into the cave. The work long predated any other cultural artifact of hominins, such as cave paintings. Since radiocarbon dating is only usable back to 50,000 years, scientists Jacques Jaubert and Dominique Genty measured the time of the works creation by analyzing uranium levels pre- and post-breakage in the stalagmites. No modern humans were in the area that long ago.^[2][3]

• http://en.wikipedia.org/wiki/Bruniquel Cave
• http://www.livescience.com/54906-neanderthals-built-bizarre-underground-ring-structures.html