Lago Mascardi is a glacially formed lake in the Bariloche Department of Río Negro Province, situated within Nahuel Huapi National Park approximately 30 kilometers south of Bariloche via Ruta Nacional 40. The lake sits at 750 meters above sea level and covers 39.2 square kilometers, with a maximum length of 15 kilometers, a maximum width of 2.5 kilometers, an average depth of 111 meters, and a maximum depth of 218 meters. Its most distinctive geographical feature is a pronounced V-shape formed by two arms: the Catedral arm, which runs roughly north-south, and the Tronador arm, which runs east-west. Isla Corazón sits near the vertex where the two arms meet. The dominant visual backdrop is Cerro Tronador, a stratovolcano whose glaciers are visible from the water. The lake's water is notably turquoise and clear.

The climate is cold and humid, with heavy rainfall and significant snowfall in winter. Paddlers should come prepared for low temperatures regardless of season, and access roads can be affected by winter weather conditions.

The primary kayak route covers the north side of the lake, launching from the area of Arroyo Fresco and Playa de los Leones and continuing approximately 25 kilometers to the Los Rápidos campsite on the Tronador arm, with a possible detour to Isla Corazón before returning. Multi-day traverses are also undertaken, with one two-day trip departing from the Campamento Educativo los Césares on the western shore, paddling to Arroyo Casalata, continuing to Arroyo La Volteada for an overnight stop, then completing the Tronador arm and circumnavigating Isla Corazón on the second day. A support vessel accompanied that group.

Several campgrounds are accessible from the water or nearby roads, including Relmu Lafquen (operated by the Wiritray Mapuche community on the north shore of the Catedral arm), La Querencia (4.5 kilometers along Route 81), and Los Rápidos on the Tronador arm shore. The Manso River is both the primary inflow and outflow. As the lake lies within Nahuel Huapi National Park, national park entrance fees may apply, and visitors are expected to follow park regulations regarding waste, fires, and camping.