Groesfaen, Pontyclun, CF72 8RT

Afon Clun is a 14‑mile (23 km) long tributary of the River Ely, situated in the counties of Cardiff and Rhondda Cynon Taf, Wales. The river’s bedrock is predominantly sandstone. It originates on the western slope of The Garth and flows south of Llantrisant, generally westward to its confluence with the River Ely at Pontyclun. Over its course the river falls 715 feet (218 m). The water is fast‑flowing, clear, shallow, and has a hard substrate. The locality of Groesfaen, within the Pontyclun postal district, lies within this river’s valley, providing a setting of natural scenery and a modest rural character. The surrounding area is defined by the river’s path and the sandstone geology of the region.