Lago Mascardi is a stunning glacial lake nestled within Nahuel Huapi National Park in the lake district of northern Patagonia, Río Negro Province, Argentina. Located approximately 30 kilometers south of Bariloche along Route 40, the lake sits at an elevation of 750 meters above sea level and takes on a distinctive V-shape or L-shape, with two primary arms — the Brazo Catedral running north to south, and the Brazo Tronador oriented east to west. The lake stretches up to 23 kilometers in length and up to 4 kilometers in width, covering a surface area of 39.2 square kilometers. Its glacial origins have produced remarkably deep, cold, and clear waters, with an average depth of 111 meters and a maximum depth of 218 meters — making it one of the deeper lakes in the region. The primary inflow is the Río Manso Superior, which drains from the Manso Glacier into the lake's northwest shore, while the outflow is also the Río Manso, which exits from the southwest shore. The lake contains two islands, including the notable Isla Corazón, located near the vertex where the two arms meet. Numerous protected bays lined with reed beds (juncales) provide critical habitat and forage for the lake's salmonid populations, making Lago Mascardi one of the premier fishing destinations in Patagonia.