Bwlch y Ddwyallt
|Bwlch y Ddwyallt|
|Gwaun Cerrig Llwydion|
|Elevation||754 m (2,474 ft)|
|Prominence||18 m (59 ft)|
|Parent peak||Waun Rydd|
|Translation||bog of the grey rocks (Welsh)|
|Parent range||Brecon Beacons|
|Topo map||OS Landranger 160|
The plateau reaches its highest point of 754m above sea level on its northern rim overlooking the head of Cwm Cwareli. The name is an odd one to apply to a peak since the Welsh word 'bwlch' generally signifies a col or pass between mountains.
The plateau is formed from the hard-wearing sandstones of the Plateau Beds Formation of the Old Red Sandstone laid down during the Devonian period. These beds directly overlie the sandstones of the Brownstones Formation, also of Devonian age, which form the bulk of the hill. The cliffs below Bwlch y Ddwyallt shows signs of having been glaciated during the ice ages as do those beneath Graig Fan Las on the eastern edge of the plateau. 
The entire area is classed as open country. The Beacons Way runs along the southern edge of the plateau. Other footpaths skirt the remaining rims of the plateau and connect with neighbouring peaks.
- Images of Bwlch y Ddwyallt and surrounding area on the Geograph website
- Nuttall, John & Anne (1999). The Mountains of England & Wales - Volume 1: Wales (2nd edition ed.). Milnthorpe, Cumbria: Cicerone. ISBN 1-85284-304-7.
- Ordnance Survey Explorer map OL12 'Brecon Beacons National Park: western area'
- British Geological Survey 1:50,000 map sheet 231 'Merthyr Tydfil' & accompanying memoir