Hillfort of a Pena dos Castros Nature · San Xoán de Río, Terra de Trives, Ourense Image of San Xoán de Río, not of the place itself. Iron Age settlement of some one hundred by seventy metres set on the western side of the valley of the river Navea, on a stretch where the channel is wedged into a canyon of very steep slopes. The surroundings are dotted with petroglyphs and rocks engraved with cup marks that document an occupation far earlier than the castro itself. Photo: xolopi (CC BY 3.0) What to see and do in San Xoán de Río