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Fire and construction

In 1990, two 176,000-year-old ring structures, several metres wide, made of broken stalagmite pieces, were discovered in a large chamber more than 300 m (980 ft) from the entrance within Grotte de Bruniquel, France. One ring was 6.7 m × 4.5 m (22 ft × 15 ft) with stalagmite pieces averaging 34.4 cm (13.5 in) in length, and the other 2.2 m × 2.1 m (7.2 ft × 6.9 ft) with pieces averaging 29.5 cm (11.6 in). There were also four other piles of stalagmite pieces for a total of 112 m (367 ft) or 2.2 t (2.4 short tons) worth of stalagmite pieces. Evidence of the use of fire and burnt bones also suggest human activity. A team of Neanderthals was likely necessary to construct the structure, but the chamber's actual purpose is uncertain. Building complex structures so deep in a cave is unprecedented in the archaeological record, and indicates sophisticated lighting and construction technology, and great familiarity with subterranean environments.