Archaeological mythology and the Welsh Triads

• One of the Three Fantastical Places of 
• Powerful Stone.........

In Wales, things come in threes.  To quote from the Prydain Wiki:

The Welsh Triads (Welsh Trioedd Ynys Prydein, literally "Triads of the Island of Britain") are a group of related texts in medieval manuscripts which preserve fragments of Welsh folklore, mythology and traditional history in groups of three. The triad is a rhetorical form whereby objects are grouped together in threes, with a heading indicating the point of likeness.

https://prydain.fandom.com/wiki/Welsh_Triads

According to Wikipedia:

Some triads simply give a list of three characters with something in common (such as "the three frivolous bards of the island of Britain" while others include substantial narrative explanation. The triad form probably originated amongst the Welsh bards or poets as a mnemonic aid in composing their poems and stories, and later became a rhetorical device of Welsh literature. The Medieval Welsh tale Culhwch and Olwen has many triads embedded in its narrative.

https://en.wikipedia.org/wiki/Welsh_Triads

I remember reading the classic work of Rachel Bromwich many years ago, and being greatly intrigued by it. What's not to like about the three princes of the Court of Arthur, or the three bulls of battle of the Island of Prydain, or the three arrogant ones, or the three atrocious assassinations, or the three great illusions?  

See also:

https://www.maryjones.us/ctexts/triads2.html

Bearing in mind that tales and myths are not necessarily old, and they they continue to be created, we come to the three Great Fabricators, Michael of the East, Robert of the Middle and Richard of the West.  And behold the tale of the Three Fantastical Places of Powerful Stone, known as Rhosyfelin, Carn Goedog and Waun Mawn..........