The rocky and wild landscape of the natural park is the result of the insistent erosion on the rock that forms it. The origin is to be found in the deposition of pebbles and other materials transported by river currents during the Tertiary period, now some 50 million years ago in an ancient delta.
Later, these pebbles would be cemented by means of a calcareous or clay matrix and would give rise to the conglomerate or pinyolenc. The erosive action of water on this type of rock has given rise to the unique relief of the park, with such characteristic elements as cliffs, canals, codines and monoliths.
At a subterranean level, the water has modelled an impressive set of cavities which, when they emerge outside, give rise to the well-known chasms, caves, burrows and upwellings. In the southern part of the park, already in the Vallès Occidental, the geological variety is more diverse: ancient materials on top of the most modern ones, remains of an ancient volcanism…
An interesting natural richness and an important architectural heritage can be seen throughout the park. From the imposing Romanesque monastery of Sant Llorenç del Munt to the most humble dry stone huts, all of this gives an idea of the important history in this territory: castles, hermitages, farmhouses and vats at the foot of the vineyard; among the most outstanding.