Beacons Reservoir is the northernmost of the three reservoirs in the Taff Fawr valley in South Wales. It is owned by Welsh Water. As its name suggests, it is located in the Brecon Beacons National Park in the Powys unitary authority area and the traditional county of Breconshire.
There is access to the Taff Trail and the Navvies Line from the car park below the dam.
During periods of low water, the remains of longhouses can be seen. One building overlooking the Taff Fawr has foundations of massive weathered slabs. Flint tools have been found.
Warning: Welsh Water advises that remains should not be approached due to the danger of deep mud.