In westernmost Neuquén, stretching from Lago Ñorquinco in the north to a diagonal that runs between Lago Nonthué on the Chilean border and Confluencia on RN 237, Parque Nacional Lanín comprises 412,000 hectares of arid steppe, mid-altitude forests ringing glacial lakes  and streams, alpine highlands, and volcanic summits. From Aluminé in the north to San Martín de los Andes  in the south, several longitudinal highways intersect graveled westbound access roads.
When the eastward-flowing Pleistocene glaciers receded, they left a series of deep finger lakes draining into the Río Limay’s upper and lower tributaries. Unlike Parque Nacional Nahuel Huapi  to the south, these lakes and the Valdivian forests surrounding them have suffered less commercial development, but they are recovering from timber exploitation and livestock grazing that persist in some areas.
Up to 3,000 millimeters of precipitation per annum supports dense humid Valdivian woodlands. Lanín’s signature species is the coniferous pehuén or monkey puzzle tree (Araucaria araucana), for centuries a subsistence resource for the Mapuches and Pehuenches (a sub-group whose name stresses their dependence on the tree’s edible nuts). Along with the broadleaf deciduous southern beech raulí, the pehuén forms part of a transitional forest overlapping southern beech species that dominate the more southerly Patagonian forests, such as the coihue, lenga, and ñire. In places, the solid bamboo colihue forms almost impenetrable thickets.
At higher elevations, above 1,600 meters, cold and wind reduce the vegetative cover to shrubs and grasses. At lower elevations the drier climate supports shrubs and steppe grasses.
Except for its trout, Lanín is less celebrated for its wildlife than for its landscapes. Fortunate visitors may see the secretive spaniel-size deer known as the pudú or the huemul (Andean deer). The major predator is the puma, present on the steppes and in the forest, while the torrent duck frequents the faster streams and the Andean condor glides on the heights. The lakes and rivers attract many other birds.
Looming above the landscape, straddling the Chilean border at 3,776 meters above sea level, lopsided Lanín is the literal and metaphorical center of Parque Nacional Lanín.
Covered by permanent snow, rising 1,500 meters above any other nearby peak, its irregular cone is a beacon for hundreds of kilometers to the east and, where the rugged terrain permits, to the north and south.
In addition to the APN visitors center at San Martín, there are ranger stations at all major lakes and some other points. While the rangers are helpful, they do not generally have maps or other printed matter. The US$8 admission fee, valid for one week, must be paid at APN and local tourist offices outside the park rather than at the park entrance.