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 consists of two waterfall-like rock formations which have been formed over thousands of years. Both cliffs rise over fifty meters from the valley floor, with one rock formation reaching down twelve meters and the other reaching thirty meters. The twelve-meter one is called "Cascada chica" (small waterfall) and "flows" from a base that is about sixty meters wide. The other, "Cascada grande" (large waterfall), extends down from a base that is about ninety meters wide and eighty meters above the valley floor.
These formations are created by freshwater 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.
The water has a temperature of 22 to 27 °C. As the water runs down the rock face, it forms large stalactites similar to those found in caves. The flow of water from the spring varies significantly between the dry and rainy seasons. 95% of the surface rock formations are of calcium carbonate; however, lower layers of both rock and water currents are little known as they are sealed by the above layers. The calcium carbonate gives the formations a white or near-white appearance, but other minerals that can be present in the water, such as silver, barium, and iron can also be found and determines the color of a particular stalactite.
In addition to the artificial pools on the Amphitheatre side, a number of other services have been built for visitors such as food stands, small markets, cabins and a regular swimming pool. The cabin area, called "Turis Yu’u," with its pool was built in the 1990s and offer areas to change clothes, shower, eat in an open-air restaurant and for overnight stays although the accommodations are very basic. This complex, as well as many of the other stalls is owned by residents of the Roeguia community.
According to the Wikipedia