DOLGELLAU

 Another Welsh name for you to practice, Dogellau! It sounds like 'Doll-geth-lee' to me. The river is the Wnion a tributary of the Mawddach.
Dolgellau is steeped in history and was formerly the county town of Merionethshire (now Gwynedd). Remnants of the 'gold rush' of the nineteenth century can still be seen and some of the gold mines can still be found, as well as a Copper Mine.