Emerging from Lago Tromen near the Chilean border at an elevation of 3,821 feet in the Eastern Andes, the Río Malleo is widely regarded as the crown jewel of northern Patagonia fly fishing. This freestone river winds approximately 30 to 35 miles southeast before joining the Río Aluminé, flowing entirely in the shadow of the snow-capped Volcán Lanín. Along its course, the Malleo transforms dramatically — from a tumbling mountain creek through boulder-strewn canyons lined with old-growth araucaria (monkey puzzle) trees, to willow-shaded runs, spring creek-like meadow sections, and open desert canyon reaches near its lower end. The river's character is greatly influenced by the volcano and the varied terrain it crosses, offering anglers an extraordinary diversity of water types within a relatively compact fishery. The Malleo holds a healthy, wild population of rainbow and brown trout and is internationally recognized for its exceptional dry fly fishing and predictable hatches, drawing anglers from around the world while remaining one of the more accessible rivers in the region.