Valles Pasiegos is an administrative comarca in Cantabria, Spain. It is formed by the valleys of the Pas and Miera rivers, each one being a natural comarca of its own.

The Pas-Pisueña valley is located in the autonomous community of Cantabria, and through it flow the Pas River and its main tributary, the Pisueña River, which joins the Pas in the township of Vargas, part of the municipality of Puente Viesgo.

In the whole valley, the repopulation allowed by the foundation of several monasteries had great importance. The most important were the San Vicente de Fístoles monastery and the Santa Cruz de Castañeda collegiate church. In addition to the monasteries, several romanesque temples were built during the 11th to 13th centuries, some of which still stand: the aforementioned Santa Cruz de Castañeda church, the Santa María de Cayón church, and the temple of San Miguel de Monte Carceña, among others. These buildings show the peak and the importance that this comarca had during those centuries.

From the 11th century on, a special, perhaps unique, human habitat began to form in the highest parts of these valleys. Its economy was based on ancient transhumant cattle breeding practices which may have been traditional to more extensive areas of Europe and the region, but which with time only survived in isolated places such as these valleys, and others elsewhere in Europe, and in Asia and Africa. The people of this habitat, who were named Pasiegans (Pasiegos) from the name of the valleys and the main river, settled mainly on the flanks of the hills of the Miera and Pas rivers. The settling was scattered, as they lived in wooden and later, stone huts (called "cabañas", cabins) which they occupied during the Spring and Summer, when the pastures were richer. For the Winter they collected enough hay to feed the cows and then moved down to the village longhouses (casas vividoras, living houses) in the valleys. The more stable population group that little by little was created along the valley-bottom roads in a street row pattern became the three Pasiegan villas: Vega de Pas, San Pedro del Romeral and San Roque de Riomiera, which are not contiguous.

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