Valleys. The rivers, generally oriented perpendicular to the aforementioned mountain ranges, form a series of valleys, short and fast in the north, towards the sea or long in the south, first narrow, then wide and finally completely open in the plains. The maritime and inland valleys correspond, one by one, in their upper part, lying on the peaks of the mountain range. The Somorrostro valley to the west and the Saizon and Ezka valleys to the east close the two series, which are linked by easy passes that are open almost all year round, except for a few days when they are blocked by snow. The valleys, as historico-political entities, cease where the Ribeira begins. Some of them have acquired great importance in local Basque history as well as offering great interest in their physical landscape: Ayala, Arratia, Baztán, Baigorri, Aezkoa, Salazar, Erronkari, Berrueza...
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