Territory is located in the central-eastern part of Cantabria, bordering the provinces of Burgos and Vizcaya. It comprises all or part of the basins corresponding to the valleys of the Miera River, the Ason River and the Soba Valley. The area encompasses a set of high geological interest sites developed on Mesozoic materials affected by tectonic processes, which have been modeled by different agents that have acted in the area throughout the Quaternary, giving rise to Glacier, Karstic, fluvial and coastal morphology.

The different elements are excellent examples of the evolution suffered by the relief, allowing to link the different evolutionary stages of the coastal zones with those of the water divisions, through the basins of the corresponding river courses. The relief is characterized by strong slopes, with heights ranging from 0 to 1600 meters above sea level.

The straight-line distance between the coast and the summit areas does not exceed 35km. The coastline extends along about 25km. It is a trimmed coast, with a predominance of cliffs, truncated by bays and estuaries, as well as beaches with dune fields. Starting from the coast inland, the reliefs are soft and with ample valley backgrounds, linked to the estuary of the Ason and the presence of saline diapiros, transforming into more abrupt reliefs. The head and middle part of the river Miera adjacent to the Ason, is characterized by common morphology related to the glaciarism that affected this area of Cantabria.