One of the few rivers with a public footpath running underneath it!
Starting as the Afon y Waun on the southern slopes of Fan Fawr, the river assumes the name of Afon Hepste when it is joined by the Nant y Cwrier. It follows a generally south-westward course to its meeting with the Afon Mellte but not before having plunged over the celebrated falls of Sgwd yr Eira.