Waterfall of Ribasieira Nature · Porto do Son, Noia, A Coruña The río Sieira crosses a rocky step in the middle of the sierra of the Barbanza, upstream of the coast to which it descends to flow out beside the beach of As Furnas; its flow shoots up with the winter rains. Photo: farrangallo (CC BY-SA 3.0) What to see and do in Porto do Son