Pistyll Rhaeadr is formed by the Afon Disgynfa falling, in three stages, over a 240-foot Silurian cliff-face, below 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. The 19th-century author George Borrow, in his book Wild Wales, remarked of the waterfall: "What shall I liken it to? I scarcely know, unless it is to an immense skein of silk agitated and disturbed by tempestuous blasts, or to the long tail of a grey courser at furious speed. I never saw water falling so gracefully, so much like thin, beautiful threads as here."
The Straining Tower built it Gothic Revival style is a Grade I listed building designed by George Frederick Deacon. Lake Vyrnwy (Llyn Efyrnwy) is a reservoir constructed in the 1880s for Liverpool Corporation Waterworks to supply Liverpool with fresh water. It flooded the head of the Vyrnwy valley and submerged the village of Llanwddyn. The Lake Vyrnwy Nature Reserve and Estate that surrounds the lake is jointly managed by the Royal Society for the Protection of Birds (RSPB) and Hafren Dyfrdwy. When the reservoir is full, it is 26 metres (84 ft) deep, contains 59.7 gigalitres, and covers an area of 4.54 square kilometres (1,121 acres), the lake has a perimeter of 19 kilometres (12 mi) with a road that goes all the way around it. Its length is 7.64 kilometres (4.75 mi).
