Aguas Termales de Sinaco rises on the Potosí Altiplano in Chile at around 38°C. This open-air thermal spring, with a pH of 7.3, offers a secluded wild bathing spot amid the high Andean plateau.
Insider tip — The Bolivian altiplano around Potosí is one of South America's most extraordinarily rich and dramatically desolate landscapes — the silver mountain of Cerro Rico above Potosí funded the Spanish Empire for centuries from the world's largest silver deposit. These thermal springs emerge from the volcanic geology of the southern altiplano, where the same geothermal forces that make Bolivia's plateau a land of geysers and mineral springs also produced the silver that once made Potosí one of the largest and wealthiest cities on Earth.