From Termas de Puyehue, Ruta 215 heads northeast up the Río Golgol valley for 17 kilometers to Anticura, before continuing to Chilean customs and immigration at Pajaritos and on to the Argentine border. At Anticura, there is camping and access to several short trails and some longer ones.

The 950-meter Sendero Educativo Salto del Indio is a signed nature trail leading to a waterfall on the Río Golgol; it takes its name from a local legend that a fugitive Mapuche hid to avoid forced labor in a colonial gold mine. An overnight excursion up the Río Anticura valley leads to Pampa Frutilla, now part of the Sendero de Chile. Areas east of Pajaritos, the Chilean border post, require Conaf permission to hike or otherwise explore because it’s a legal no-man’s land and, unfortunately, this means limited access to large parts of the park.

From El Caulle, two kilometers west of Anticura, a 16-kilometer trail climbs steeply to the flanks of Volcán Puyehue, where there’s a simple refugio and camping is also possible; alternatively, continue through a barren volcanic landscape of fumaroles and lava flows to rustic thermal pools where it’s also possible to camp.

At the trailhead, though, ex-UDI senator Marcos Cariola’s Turismo El Caulle (Ruta 215, Km 90, tel. 099/6412000, www.elcaulle.com) demands a US$16 toll for the right to pass through his property; this includes use of the refugio, but Cariola’s cattle have badly eroded parts of the trail. It’s possible to hike through to Riñinahue, at Lago Ranco’s south end (where there’s a smaller US$4 toll) rather than return to El Caulle.

Volcán Puyehue itself is a flat-topped Holocene caldera, measuring 2.4 kilometers in diameter; it sits within a larger caldera measuring five kilometers across. The most recent eruptions have come not from the summit caldera, but from vents on its western, southern, and eastern flanks, and a small cone on the southern flank.