Caviahue

Caviahue sits high inside the outer caldera of the Copahue volcano, in a landscape that smells of sulphur, steams from the ground, and holds a crater lake so acidic — pH below one — that only extremophile bacteria survive it. Waterfalls stair down through araucaria country toward the village, thermal water rises hot enough to need dilution before anyone soaks in it, and in winter ski slopes open on the caldera's flanks above the steam.

The volcano remains genuinely active, with periodic ash emissions — current volcanic and access notices govern the thermal settlement and the higher routes, and the village is the year-round base beneath them. Two lakes tell the geology: Lago Caviahue, glacial and ordinary in its chemistry, and the vent lake on Copahue itself, among the most acidic crater lakes on Earth and warm as a bath. The thermal complex has treated joint and skin conditions since the nineteenth century, its sulphur pools and mud peloids drawn from the volcanic system through the operating facilities — while out on the geothermal fields like Las Máquinas, steam vents through fractured, ash-coloured ground where marked routes are the rule and visible steam never makes informal bathing safe. The araucaria stands around the caldera include trees centuries old, protected by law.