It is a thermal complex located in the commune of Machalí (Chile) on the banks of the Cachapoal River and 31 km east of the city of Rancagua, at an altitude of 760 meters above sea level and close to the Río de Los Cipreses National Reserve. The temperature of its hot springs ranges between 42 and 48 °C and they contain, among other elements, bicarbonate, chlorine, lithium, magnesium, oxygen and potassium, which has made them famous for curing arthritic, rheumatic, and skin conditions. and respiratory. It is a historic place, since these hot springs were known by the natives of the place before the arrival of the Spaniards and later visited by the managers of the country's independence such as José de San Martín and the Father of the Nation, Don Ambrosio O'Higgins. , also visited later by several presidents of the republic.