Protecting a glorious chunk of the Andean cordillera and its neighbouring steppe, most of the park falls within the watershed of the immense Lago Nahuel Huapi, an impressive expanse of water that can seem benign one moment and a froth of seething whitecaps the next. Of glacial origin, it’s 557 square kilometres in area, but highly irregular in shape with peninsulas, islands and attenuated, fjord-like tentacles that sweep down from the thickly forested border region. The lake’s name comes from Mapuche for Isle (huapi) of the Tiger (nahuel) and refers to the jaguars that once inhabited regions even this far south. Heavy rainfall permits the growth of temperate rainforest and species such as the alerce, here at the northernmost extent of its range in Argentina. Other species typical of the sub-Antarctic Patagonian forests also flourish: giant coihues, lengas and ñire among others. The dominant massif of the park is an extinct volcano, Cerro Tronador, whose three peaks straddle the Argentine–Chilean border in the south. Glaciers slide off its heights in all directions, though all are in a state of alarmingly rapid recession.
Snow can fall as late as December and as early as March at higher altitudes: it’s not advisable to hike certain trails outside the high season. Bear in mind the area is a long way west of Buenos Aires despite being in the same time zone, so the sun is overhead in summer closer to 3pm, rather than midday. Average temperatures are 18°C in summer and 2°C in winter. The strongest winds blow in spring, which is otherwise a good time to visit, as is the calmer autumn, when the deciduous trees wear their spectacular late-season colours.