Swallow Falls (Rhaeadr y Wenol in Welsh) is a renowned tourist spot. Below the falls is a deep pool that is said to hold the soul of Sir John Wynne of Gwydir (see Llanrwst) - who interestingly was a member of parliament in 1596 - as a prisoner. This cruel man is to be held there until doomsday.
For further information, please read Haunted Wales by Peter Underwood.