Location
A strong contender for its location would be Penrith, Cumbria, known as Penrhudd in modern Welsh. King Arthur's Round Table, Cumbria by Penrith, is a Neolithic henge. Another possibility supported by Rachel Bromwich, the latest editor of the Welsh Triads, is a location somewhere near the Rhins of Galloway and Stranraer. This would match the importance of St Mungo in that area. Both these places would have been in Rheged.
One researcher suggests it is actually in north Wales at Morfa Rhianedd, near Llandudno, but this is contrary to tradition.
Read more about this topic: Pen Rhionydd