Oiartzun (river)

The Oiartzun River is a short river in the Basque Country in the north of the Iberian Peninsula. It is the smallest river of Gipuzkoa flowing into the Bay of Biscay (Atlantic basin); the river joins the sea at the Bay of Pasaia. The Oiartzun rises in the Aiako Harria massif at an altitude higher than 700 m. It flows down through steep slopes and falls, with an average drop to its mouth of 5.49% (600 m drop in the first 5 km).