Hierve el Agua (Spanish for "the water boils") is a set of natural travertine rock formations in San Lorenzo Albarradas, Oaxaca, Mexico that resemble cascades of water. The site is located about 70 km east of Oaxaca City, and consists of two rock shelves or cliffs which rise between fifty and ninety metres from the valley below, from which extend nearly white rock formations which look like waterfalls. These formations are created by fresh water springs, whose water is over-saturated with calcium carbonate and other minerals. As the water trickles over the cliffs, the excess minerals are deposited, much in the same manner that stalactites are formed in caves. One of the cliffs, called the "cascada chica" (small waterfall) or the Amphitheatre, contains two large artificial pools for swimming as well as a number of small natural pools. One of the artificial pools is very near the edge of the cliff.