Extension, location and municipalities:
The LIC of the Oriental Mountain has 21,679 ha along the rock masses of Hornijo, Alto Asón and Valnera, involving the municipalities of Soba, Ruesga, Arredondo, Vega de Pas, San Roque de Riomiera, Miera and Ramales de la Victoria.
The group is a transition area between high, alpine mountain and Cantabrian mid-mountain, only existing in the higher altitudes of Valnera. The weather is humid with regular rains, no summer dryness and with maximum temperatures in winter and spring.
Temperature is moderated, reaching severe levels during winter with less than 2ºC in January above 1,600 metres and a higher snow temperature than in the other Pas valleys.
Snowmelting reaches extraordinary levels in some years, with enormous quantities in the mass of Valnera and fast fusion processes in situations of southern wind or early spring which signifies important apportions to nearby rivers.
Aside from the ecosystem values, ther are two features of the zone should be pointed out: the living geomorphology of the area with intense karstifications and complex glacier origins and a marked landscape personality given by the development of the settlement and exploitation model of its inhabitants.