THE REAL LOCATION OF CAER ARIANRHOD

Pen Y Garreg Hillfort

Caer Arianrhod

The Route From Dinas Dinlle to Caer Arianrhod

Pen-Y-Garreg (= Caer Arianrhod?)

The identification of Caer Arianrhod of the MABINOGION tale 'Math Son of Mathonwy' with a small group of rocks (part of a submerged reef) off the coast of Arfon has long been held traditionally.  And, indeed, at least one reference to the place in that story would suggest this goddess's fort had to be reached by water.  We are told in the relevant episode that Gwydion and Lleu left Caer Dathal and walked along the coast between there and Aber Menai.  They then sailed from there to Caer Arianrhod.

Conclusive as this may seem, there is a rival account for the fort's location in the very same story.

We are told that Gwydion and Lleu leave Dinas Dinlleu (D. Dinlle) and travel first to Brynaerau and then to Cefn Clun Tyno (http://www.nantlle.com/mabinogi-saesneg-places-mentioned-in-the-fourth-branch.htm). From the Tyno site they ride to Caer Arianrhod.  We can see immediately the problem this account poses when we view the map.  They have traveled well past the rocks of C. Arianrhod.  The Tyno place-names are concentrated only a very short distance from the Pen-Y-Carreg hillfort:

https://coflein.gov.uk/en/site/302372/details/pen-y-garreg-hillfort

Their journey also took them past the Y Foel hillfort (well to the WSW, in fact):

https://coflein.gov.uk/en/site/95338/details/y-foel-camp

How are we to reconcile these two opposing geographical placements of Caer Arianrhod?

Well, I don't think it's difficult to imagine that as the story was told and retold over the centuries, different strands of tradition were accidentally retained, sometimes literally side by side. As the offshore rocks are in no sense a fort, it may well have been considered at some point in time a sort of Otherworld location.  On the other hand, Pen-Y-Carreg would represent an actual settlement imprinted on the ancient landscape.