The dividing line between the Saja and the Besaya is formed by mountains with rounded shapes of medium altitude which are gaining height upon approach of the Cordillera at its southern end with Campoo.

[3] In terms of geology the conglomerates of "acastilladas" and reddish formations, called the "Molinucos del diablo" along Canal de Cureñas are some of the most visited points of interest.

Morphological features include the fluvial with remains of glacial formations south of the Sierra del Cordel of the Cantabrian Mountains.

The forest is characterized by a diversity of trees and associated shrubs such as chestnuts, ash, maples, hazelnuts, honeysuckle, and varied flowering and herbaceous plants.

Among fish, the common trout is the dominant species[3] The Iberian wolf is not very rare, and brown bears have been sighted, thus considering this zone as an important nexus of communication between isolated populations of this plantigrade.

[citation needed] The park has a visitor center and six recreational areas named "La casa del Monte" in Ucieda, "Llano Castrillo" in Bárcena Mayor, "Cambillas" in Saja, "Cieza" in Cieza, "El Prauco" and "El Vaho" in Los Llares and the view point "La Cardosa", located on the CA-280 in direction of the port of Palombera, 4 km from the top at an altitude of 1000 meters.