The park is home to the black vulture and the Spanish imperial eagle, as well as many small mammals and amphibians.

Close by and to the south is the Cliff of Carnations, which being 2.388 kilometers above sea level is the second-highest peak in the Sierra de Guadarrama.

The peaks of the park, ordered from north to south, are the following: One of the most interesting elements of the reserve is the Peñalara cirque, created by a glaciar.

Each has a moraine at its lower part, a rocky zone with a relatively gentle slope that was produced by the track of an ancient glacier.

During the wet seasons (fall and spring), a series of arroyos flow from the major lakes and often form cascades, which add to the landscape's beauty.

The high relief of the reserve is due to the collision between the tectonic plates corresponding to the North and South Subplateaus.

In the Middle Paleozoic (360 to 290 mya (unit)), an initial substrate of ancient granites and sediments began to fold and metamorphose, creating the gneisses.

In this last period occurred a monumental departure from the ocean, which left subaquatic zones exposed on the surface (prior to this, it is likely that the sierra was not more than an islet raised slightly above the sea) and formed sinks of sediment that covered the plains with sediment and would give them their later calcareous character.

In the Cenozoic (66 to 1.8 mya), the processes that raised the Peñalara massif and divided it into the blocks we find today began to work again.

Glacial action in the Quaternary (1.8 mya to present) finished shaping the Peñalara cirque and the walls of the mountainous axis.

The cold climate, the strong wind, and the abundant snow during most of the year are the reasons why forests only grow at low altitudes and the fauna is composed of small animals.

The dominant vegetation is a matorral of broom and jabino, which alternates with meadows of Nardus stricta in wetter areas like the cirque basins.

Among the Lepidoptera are the butterfly Parnassius apollo, the plebicula ni ecensis, and the moth Hyphoraia dejeani.

Peñalara Nature Reserve has a mountain climate characterized by very cold winters and mild summers.

An information building at Puerto de Cotos dispenses maps of trails and safety rules.

The tourism center also holds a restaurant, the headquarters of the Spanish Alpine Club, a mountain-climbing school, and a sled rental.

At the foot of the Older Sister, some 300 m south of Peñalara Great Lake and 2.075 km high, is the obsolete Zabala mountain shelter, which is now used only for storage of maintenance supplies.

The hotels and lodges nearest to Peñalara Nature Reserve are in Puerto de Navacerrada and the town of Rascafría.

Extra precautions are needed in winter, when the bad weather and thick snow and ice make for hard travel and easy disorientation.

On 15 June 1990 the Community of Madrid declared the zone a Natural Park of the Peak, Cirque, and Lakes of Peñalara by the law 6/1990.

From 1998 to the beginning of the 21st century, the old Valcotos ski resort that occupied a large part of the protected area was dismantled.

At the beginning of the 21st century, the Community of Madrid together with Castilla y León declared that a large portion of the sierra would form a Guadarrama National Park.

Paradoxically, the protection of the natural park risked being reduced, as the President of the Community of Madrid wished to promote hunting in the sierra.