Gruta do Lago Azul Natural Monument

The Gruta do Lago Azul has a main hall with a floor that slopes to a subterranean lake over 50 metres (160 ft) long. The entrance is circular, about 40 metres (130 ft) in diameter, illuminating the lake with sunshine. Between the months of September and February the waters take on an intense blue color, for which the lake is named. Fossil bones have been found of large mammals that inhabited the region for more than 12,000 years in the Pleistocene. These include giant sloths, armadillos and sabre-toothed tigers.