Source of the Ulla River Nature · Antas de Ulla, Ulloa, Lugo Image of Antas de Ulla, not of the place itself. The Ulla river rises in the parish of Olveda, in Antas de Ulla, although the exact place of its source varies depending on the source consulted. Its name is thought to derive from the Indo-European root wel-, 'to turn', 'swirling water'. From its source it runs 132 kilometres, separating the provinces of A Coruña and Pontevedra except for two short stretches in the municipalities of Vedra and Padrón, before flowing into the ria of Arousa; its basin, covering 2,764 square kilometres, is the second largest in Galicia after that of the Miño river. Its main tributaries are the Arnego and the Deza, and along its course lies the Portodemouros reservoir, one of the most important hydraulic works of its time. Photo: José Antonio Gil Martínez from Vigo, Spain (CC BY 2.0) What to see and do in Antas de Ulla