The Nant Llech is a minor river in Powys, Wales and which lies wholly within the Brecon Beacons National Park.
[1] The most famous feature of the river is Henrhyd Falls (Sgwd Henrhyd or Rhaeadr Henrhyd in Welsh), a 27m/90 ft high fall where the river plunges over the edge of a band of hard sandstone known as the 'Farewell Rock' into a deep plunge pool.
The river continues below in a steep wooded gorge cut into mudstones and sandstones of the Carboniferous age Coal Measures.
[2] The falls are owned and managed by the National Trust which provides a free car park off the minor road between Coelbren and Pen-y-cae for visitors wanting to explore the area.
[3] Sir William Edmond Logan, first director of the Geological Survey of Canada discovered some fossil trees near the base of the falls.