This is a spectacular medium-sized river averaging 60-90 feet in width, perfect for the wading angler, and recognized as an outstanding dry fly angling destination. It has the character of a spring creek; its currents are slow and the fishing can sometimes be technical requiring small flies and tippets, and delicate presentation. It supports healthy populations of naturally reproducing rainbow and brown trout averaging 15-19 inches, with many opportunities for larger fish. It originates at Tromen lake, high in the Andes. Nestled in the folds of the Lanín Volcano (12390 feet) and surrounded by millenary monkey puzzle tree forests, it flows to the east for 30 miles to join the Aluminé River. Most of the river flows along the Olsen family ranch, which allows guests staying at San Huberto Lodge to experience unique and easy access to Malleo river´s pools.