National Parks in Neuquén Province
The area of Neuquén and Río Negro is mostly protected as a National Park to preserve some animal and plant species. Information about fees, how to get there and what activities are offered is available here. These are the four main National Parks.
Nahuel Hualpi National Park

It is the oldest park, it was established in 1934, and also the largest in the area. It surrounds the lake with the same name, covers the border between the two provinces and has its limit in the border with Chile. Many people have claimed to see a little monster in the lake and they call it Nahuelito, just like it happens with the Ness monster in Scotland or the Banyoles monster in Catalonia.
The park has three of the main landscapes of Argentina. In the lower parts of the park there is the Patagonian steppe, at a higher altitude there is the temperate rainforests and at the highest you can find the Altoandino, where there are glaciers and all-year snow.
The zone was volcanic and there several extinct volcanoes like the Tronador. Some of the most accessible mountains to go trekking or hiking are the Cerro Catedral and the Cerro Tronador.
Laguna Blanca National Park
It surrounds the lake Laguna Blanca and is located in the west of the province. It was created in order to preserve a very concrete swan specie: the black-neck swan.

It has an arid and windy climate and it is famous because of the Prehistoric paintings you can see in the Salamanca Caves. Other objects have been found there from the Mapuche indigenous tribe that used to inhabit there.
Lanín National Park

It is pretty similar to the Nahuel Hualpi one in terms of fauna, flora and climate. But this one has more than twenty alpine lakes that were created as a result of the glaciations. It is called Lanín because of the big volcano named the same that is also part of another National Park in Chile. It is not known, though, when was it active for the last time.
Los Arrayanes National Park
It is the last one but the most especial. It is located inside the Nahuel Hualpi Park, in the Quetrihué Peninsula and has the biggest arrayanes forest in the world. It has some 600-year-old trees. Although it was already protected, it was renamed and declared a separate park in order to protect this tree specie.

There is a 80 pesos fee to go in, and you have to be back at the entrance by dusk.