The Sierra de Guadarrama has a wide geological diversity, according to its soil composition and its origin. The range goes from 500 million years old rocks, as gneissic ones, to more recent sedimentary accumulations, as for example the limes, sands, and gravels the water courses system provides, or the Quaternary glaciers formations, that modelled the landscape on circuses, moraines and high mountain lakes. In addition, the granite batholith from La Pedriza, is very relevant, since it has been designated a Geological Point of Interest and a Biosphere Reserve, remaining a unique and singular formation in the Iberian Peninsula.

Although these sites currently belong to the Sierra de Guadarrama National Park, their earliest protection status goes back to 1930, when La Pedriza along with the Summit, Peñalara Cirque and Lakes were declared Natural Sites of National Interest.

The vestiges of Quaternary glacier and the current periglacial processes can be observed in Peñalara Massif. Much of the current geomorphology is explained by these processes, occurred thousands of years ago, but they have currently resulted in a great diversity of species and habitats and in a high landscape quality.

La Pedriza is a particular mountain landscape, unique in the Iberian peninsula. Located in the Southern slope of the Sierra de Guadarrama, its topography is defined by a collection of amazingly shaped rocks and crags. It consists of a granite batholith, about 3.200 h wide, which formed in Paleozoic era, -in the carboniferous period- as result of the Hercynic orogeny (280 to 345 million years).

La Pedriza can be considered as a sierra having its own organization. The Eastern section is bordered by the Collado de la Ventana and the Collado de la Dehesilla hills. Its Western limit are the Cuerda de las Milaneras, La Pedriza circus, the Dehesilla stream source area, and the Peña del Yelmo, which is the highest spot in the South Western block. The Riscos de las Torres (2.029m) is the maximum height in La Pedriza.