The park around the lagoon was created in 1940 to protect the lagoon and particularly the population of black-necked swans (Cygnus melancoryphus). It has an area of 112.5 km². The lagoon is situated in the Patagonian steppe, surrounded by hills and gorges.
It has important aquaticbird fauna, of several species and in great number.
The lagoon used to host the largest known subpopulation of the endemic Patagonia frog (Atelognathus patagonicus), but this has been extirpated by introduced predatory fish; the species survives in isolated ponds in the buffer zone of the national park.
Near the lagoon is the Salamanca cave, historically inhabited by humans, where rock paintings, typical of northern Patagonia, can be seen. Other mapuche and prehistoric human artifacts have been found in the park.