Deep in the Patagonian Andes of Río Negro Province, Argentina, the Río Manso is one of the most remarkable and pristine trout fisheries in South America. Originating from the Ventisquero Negro glacier on the eastern flanks of Mount Tronador — the highest peak in Nahuel Huapi National Park at approximately 11,500 feet — the river flows through a glacially carved valley, connecting a chain of stunning mountain lakes before eventually crossing into Chile and emptying into the Pacific Ocean. The entire Argentine portion of the river flows through Nahuel Huapi National Park, the first national park established in Argentina. Located just 90 minutes southwest of San Carlos de Bariloche, the Río Manso remains remarkably uncrowded despite its proximity to a major city, largely due to its inaccessibility. The river's crystal-clear waters, old-growth Andean forest, and the snow-capped backdrop of Mount Tronador create an angling environment that rivals the finest trout streams anywhere in the world.