This beautiful day trek, which should be possible in around eight hours, is easy enough to do on your own, leaving from Copahue. Due to snow conditions, it’s only possible from December to April unless you bring special equipment. Caviahue Tours is among the many operators offering guides on this route.
From the Hotel Valle del Volcán at the upper (southwest) edge of the village, cross the little footbridge and climb briefly past a life-size statue of the Virgin. The well-worn foot track leads across a sparsely vegetated plain toward the exploded cone of Volcán Copahue, dipping down to lush, green lawns by the northern shore of the Lagunas Las Mellizas’ western ‘twin.’ Follow a path along the lake’s north side past little black-sand beaches and gushing springs on its opposite shore, to reach the start of a steam pipeline, one to 1¼ hours from the village. The roaring of steam from the subterranean Copahue Geothermal Field entering the vapoducto and irregular explosive blasts of discharging steam can be heard along much of the trek. Cross the lake outlet – further downstream is a wide, easy ford – then cut up southwest over snowdrifts past a tarn to meet a 4WD track at the edge of a small waterlogged meadow. Turn right and follow this rough road up around left (or take a vague trail marked with white paint splashes to its right until you come back to the road on a rocky ridge below a wooden cross). The 4WD track continues westward up through a barren volcanic moonscape to end under a tiny glacier on the east flank of Volcán Copahue, 1¼ to 1½ hours from the pipeline.
Ascend southwest over bouldery ridges, crossing several small mineral-and-meltwater streams. To the northwest, in Chile, the ice-smothered Sierra Velluda and the near-perfect snowy cone of Volcán Antuco rise up majestically. From the third streamlet (with yellowy, sulfur-encrusted sides), cut along the slope below a hot spring, then climb to the top of a prominent gray-pumice spur that lies on the international border. Ascend the spur until it becomes impossibly steep, then traverse up rightward over loose slopes into a gap to reach Laguna Termal, 1¼ to 1½ hours from the end of the 4WD track (3½ to 4¼ hours from Copahue).
Filling Volcán Copahue’s eastern crater, this steaming hot lake feeds itself by melting the snout of a glacier that forms a massive rim of ice above its back wall. Sulfurous fumes often force trekkers to retreat from the lake, but these high slopes also grant a wonderful vista across the vast basin (where both villages are visible) between the horseshoe-shaped Lago Caviahue (Lago Agrio) and the elongated Lago Trolope to the northeast. From here, more experienced trekkers can continue up to the summit of Volcán Copahue.
If you’d like to take the side route to the peak of Volcán Copahue, it’s recommended that you go with an experienced guide.
To get back to Copahue, retrace your ascent route. If you have a decent map of the area, you can follow the Arroyo Caviahue (Río Agrio) and RN 26 back to town.