I feel that the overall effect of this video expresses quite an intense and scary atmosphere.
Info from Wiki:
Pistyll Rhaeadr is formed by the Afon Disgynfa's falling, in three stages, over a 240-foot (73 m) Silurian cliff-face, after which the river is known as the Afon Rhaeadr. The tallest stage is estimated at about 40 metres. It is counted as one of the Seven Wonders of Wales and is a Site of Special Scientific Interest.