This municipal natural site has been defined as such since 2005 and is located in the municipality of Castell de Castells, in the area of La Serra de La Serrella. It stands out because of its rugged orography, with mountains that reach altitudes greater than 1,300 metres above sea level. Most of the area has steep slopes separated by small ravines. The area of crags and rock walls is characterised by a very steep relief, with the presence of numerous ridges.

One of the most representative parts of the morphology of the area is the presence of Els Arcs, a monument in the midst of nature that gives the place its name. Els Arcs are two natural rock arches of great geological interest.

In addition, the space is framed by some impressive mountains, among which the majestic Penya del Castellet stands out, with more than 1,000 metres of altitude, at the top of which the remains of a Muslim castle are preserved and L’Esbardal de Miquel El Serril, a set of cave paintings, composed of two rock shelters with various iconographic motifs that alternate with Levantine-type art. They are considered World Heritage elements, included in the cave art of the Mediterranean basin. Both are listed as Béns d’Interés Cultural (Assets of Cultural Interest).

Regarding the fauna, the presence of threatened species stands out, among which there are birds of prey such as the Bonelli’s eagle, the golden eagle, the peregrine falcon and the long-eared owl; reptiles such as the green snake, the ocellated lizard or the Iberian viper; and mammals such as the European hedgehog, the greater white-toothed shrew and the beech marten.

As for the flora, there are pine forests and small forests of holm oaks, interspersed with some specimens of field maple, ash and Portuguese oak. Also noteworthy are the rupicolous plant communities, among which are species of high interest for conservation reasons.