Lago Argentino, 185 meters above sea level, is 125 km long and 14-20 km wide totalling and area of 1,560 km2. This makes it the largest lake in Argentina and the third largest in South America. Its depth ranges from 35 to 1000 meters; in the middle, across from Península Avellaneda, and in the south bank, it is 300 meters deep.

It is made up of a main body and some branches, like the Upsala, Norte, Rico and Sur. These last two branches are joined to the main body through the Canal de los Témpanos, which flows past Perito Moreno Glaciar into the Lake.

The Santa Cruz River is born in this lake and flows east into the Atlantic Ocean. Its special color is due to the quicklime (calcium oxide) produced by glaciar erosion.

In 1873, sailor Valentín Filberg arrived at the lake and thought it was the Viedma Lake, discovered by Antonio Viedma in 1782. Four years later, Francisco P. Moreno and Carlos Moyano arrived at the same spot, they verified it was a different lake and named it "Argentino" on 15 February 1877.

Today it is sailed  by boats that leave either from Puerto Bandera, 45 km. away from El Calafate, and from Bajo de la Sombra, and go along Canal de los Témpanos and into the Norte, Upsala and Rico branches.