The highest waterfall in South Wales is tucked away on the western edge of the Brecon Beacons. Plunging 90ft (27m) into a wooded gorge, Henrhyd waterfall is a spectacular sight and the surrounding Graig Llech Woods are a haven for wildlife. The falls occur on a geological fault on the river Nant Llech and have retreated up the valley by up to 165ft (50m) since the last Ice Age. The hard layer of sandstone forming the lip of the waterfall is known as Farewell Rock. Coal miners digging down to this layer in the mines of the South Wales valleys would say 'farewell' as there was little chance of finding coal below it. In the mid-1800s the area was surveyed by William Logan, an internationally noted geologist. While surveying for a detailed geological map of the South Wales coalfields he found two fossilised trees at the base of the falls. You can now see them outside Swansea museum.
