Mascardi Lake is V-shaped with two arms roughly equal in length and width. The eastern arm is called the Catedral (Cathedral) arm and the western arm is called the Tronador arm, named after the volcano on the border with Chile which is the highest and most prominent mountain in the area. The lake is surrounded by mountains rising steeply from the lake to elevations of more than . The mountains are snow-capped most of the year. Timberline on the mountains is above . The lake has a maximum depth of and a surface area of