River Altube or Barambio. It rises in the Altube steps, in the western foothills of Gorbea. In its upper basin it receives the waters of the Rekandi, Berganza and other smaller streams. It enters Biscay, near Arbaiza (V), opposite Mount Bardaola (A) and irrigates the Orozco valley. In its last stretch, it serves as a boundary Alava and Biscay, receives the Aranguti stream (A) and joins the Nervión at Areta.