Casoio River Nature · Carballeda de Valdeorras, Valdeorras, Ourense Image of Carballeda de Valdeorras, not of the place itself. A river that rises at the confluence of the Valborrás and Riodolas rivers, in the Sierra do Eixe, at 1,440 metres above sea level, and runs 19.5 kilometres from south to north, entirely within the concello of Carballeda de Valdeorras, before flowing into the Sil at Sobradelo. It gives its name to the parish of Casoio, and its valley holds both slate quarries, the remains of Roman mining, and the yew grove of Casaio. It is a mountain river with an incised course that opens into small floodplains, such as that of the hermitage of San Cosme y San Damián, where a pilgrimage is held in late September. It historically served for trout fishing and as motive power for mills; in 1971 the Casoio reservoir was completed at Sobradelo, to produce electric power. Photo: Estevoaei (CC BY-SA 4.0) What to see and do in Carballeda de Valdeorras