Deep Neanderthal construction
Deep inside Bruniquel Cave in southwestern France, 336 meters from the entrance, lies one of the oldest known human-made constructions. In a large chamber, early Neanderthals built six structures entirely from broken stalagmites. Two are large rings, while the other four are smaller piles or accumulations. The project involved breaking and moving approximately 400 stalagmite pieces, collectively weighing an estimated 2.2 metric tons.
The main ring is an ellipse measuring 6.7 by 4.5 meters, with a smaller ring nearby measuring 2.2 by 2.1 meters. The pieces, technically called "speleofacts," are arranged in up to four stacked layers, reaching a height of about 40 centimeters. The builders deliberately calibrated the pieces, selecting fragments with an average length of about 30-34 centimeters. Some stalagmites were set vertically against the rings, possibly to act as reinforcements. This entire construction effort happened in the phreatic zone, a part of the cave that receives no natural light.