In the northest part of Palencia, near the borders with Cantabria and León, is located the National Reserve of Fuentes Carrionas y Fuente Cobre, a natural scenery of exceptional beauty. This mountainous area includes remarkable glacial morphologies. The park, with a total area of 80,000 h, covers ten municipalities: Aguilar de Campoo, Brañosera, Castrejón de la Peña, Cervera de Pisuerga, Dehesa de Montejo, La Pernía, Polentinos, San Cebrián de Múda, Triollo and Velilla del Río Carrión.

The reserve, unknown to most people, offers a broad variety of landscapes, from the high peaks of Curavacas, Espigüete, Pico Murcia, Tres Provincia; to Quaternary glacial lakes and cirques such as the Pozo de las Lomas, Pozos del Ves and the sources of the rivers Carrión, at Fuentes Carrionas, and of the Pisuerga at Fuente Cobre. The area also contains several lakes, such as the Compuerto, Camporredondo, Requejada, Ruesga and Aguilar.

The vegetation varies acconding to the different landscapes, but predominates the Caducous forest of beeches and oaks, especially at Fuente Cobre. There are also pines, holm oaks, specimens of the Juniperus thurifera and yews, an endangered species. Starting from the 1,600 metres of altitude can be found junipers and, depending on the type of soil, heathers and other bushes (Arctostaphylos uva-ursi, Daphne laureola). Between the 1,500 and 500 metres of altitude appear the heathers.

As regards to the fauna of the reserve, the variety is similar to that of the vegetation. The peaks are home to chamois and birds (Passer montanus, Trichodroma muraria and Pyrrhocorax graculus). The Pyrrhocorax graculus, the most abundant of the three, is a corvine of black feathers and yellow beak that usually flies in flocks. The peaks are also home to royal eagles, vultures and eagle owls. The forests are inhabited by brown bears, wolfs, deers, roe deers, capercaillies, wild boars, garden dormouses and martens. In the rivers and lakes can be found otters and the Galemys pirenaicus.