Pwll y wrach signifies pool of the witch in Welsh

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

. It is a feature on the River Ennig

Afon Llynfi (Wye)

The Afon Llynfi is a short river in the county of Powys, south Wales. A tributary of the River Wye, it runs approximately south to north just to the west of the Black Mountains and partly within the Brecon Beacons National Park. The river rises as a small stream to the west of the village of Bwlch...

 near Talgarth

Talgarth

Talgarth is a small market town and community in southern Powys , Mid Wales, with a population of 1,645. Notable buildings in the town include its 14th-century parish church and 13th century Pele Tower, located in the town centre, now home to the Tourist Information and Resource Centre...

 in south Powys

Powys

Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

. The river plunges in two separate streams over a lip of hard rock (the Bishops Frome Limestone and formerly known as the Psammosteus Limestone) into a pool scoured in the softer mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

s of the underlying Raglan Mudstone Formation.

The feature occurs within Cwm Pwll-y-wrach, a deep wooded valley which is managed for its resident dormouse

Dormouse

Dormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...

 population by the Brecknock Wildlife Trust

Brecknock Wildlife Trust

Brecknock Wildlife Trust is a wildlife trust covering the vice county of Brecknockshire in Wales. The offices of the Trust are located in Brecon. The Trust has 21 reserves, the majority of which are in the Brecon Beacons National Park. -External links:...

which has established a nature reserve at the site. The Trust has established trails within the wood to enable public access.

It is suggested that the name derives from the ancient practice of ducking witches in the plunge pool.