The Pehuenche - "people of the pehuén" - take their name from the araucaria tree, the spiky, prehistoric conifer whose pine nuts have sustained Andean families for thousands of years. They are one branch of the larger Mapuche nation, and in Alto Biobío they remain the overwhelming majority, roughly 86 percent of the commune, scattered across a dozen communities along the Queuco and Biobío rivers with names like Cauñicu, Pitril, Butalelbun, and Ralco Lepoy. Autumn still means the piñoneo, the gathering of araucaria seeds, families climbing into the high forests to harvest a food older than any empire and carrying it back down for the winter. In the small capital of Ralco, a Pehuenche museum keeps the culture not as a relic behind glass but as something living - woven textiles, the Mapudungun language still spoken in the valleys, the memory of the land held by the people who never left it.

The Biobío was once one of South America's great wild rivers, a torrent prized by kayakers worldwide for its rapids. Then came the dams. The Ralco hydroelectric project, completed in the mid-2000s, raised a 155-meter wall across the upper river and drowned some 3,400 hectares of valley - homes, farms, and ancestral cemeteries vanishing beneath a new lake. Roughly ninety Pehuenche families were displaced. Most signed agreements and relocated. Seven families refused. Among them were the Quintremán sisters, Nicolasa and Berta, who became the unbending face of the resistance. They argued, simply, that the land was not theirs to sell, because it belonged to their dead and to those not yet born.

The struggle outgrew the valley. International rights groups took up the cause, and the case reached the Inter-American Commission on Human Rights, which in 2003 pressed Chile to answer for how it had treated the Pehuenche - though by then the dam was nearly finished. Nicolasa and Berta Quintremán together won the Petra Kelly Prize and the recognition of activists around the globe. The water rose anyway. When she drowned in the reservoir in December 2013, Chileans across the political spectrum understood the bitter symmetry: the woman who fought the lake had been claimed by it. Her resistance did not stop the dam, but it changed how a nation talks about whose land the rivers run through.

For all its history, Alto Biobío is first a place of staggering Andean wilderness. Two active volcanoes brood over the commune. Callaqui rises in a long ridge above the river, while Copahue, straddling the Argentine border, vents sulfurous steam and erupted as recently as 2013, sending villagers fleeing under a red alert. Glacial lagoons - El Barco, La Mula, Pirquinco - mirror the peaks in cold blue. The araucaria forests that gave the Pehuenche their name climb the slopes, some trees standing for over a thousand years. Tourism here is built around the communities themselves: not a backdrop to be photographed, but hosts who decide how their home is seen.