There is another wonderful thing in the region which is called Bucit. There is there a mound of stones and one stone placed on top has a footprint of a dog on it. When hunting the porker Troynt, stamped Cabal (who was the dog of the soldier Arthur) the step in the stone, and afterward Arthur gathered together stones under the stone on which was the track of his dog, and it is called Carn Cabal. And men come, and they take the stone in their hands through the space of the day and night, even so, in the daylight of the following day it is come upon on top of his collection."1,2
The wonderous cairn mentioned is almost certainly one of those on the mountain Carn Gafallt, in the Elan Valley, which used to be in the early medieval cantref3 of Builth*. It seems that either the cairn was so famous it gave its name to the whole hill, or, just as likely, the myth was adapted to explain the name4,5. The hill has three prominent burial mounds near the top, probably from the bronze age6, made from local rock. The rock is a conglomerate (a rock made from pebbles of other rock, held together by a cement-like filling). This easily releases its pebbles to form hollows and, not wishing to cast aspersions on the legend, with the eye of faith it is hard not to find a dog's footprint if you go looking for it (see Visit Details). The first modern to make the association between the mountain and the wonder, Charlotte Guest, gave this account of just such an experience.
Read more about the Science of this wonder, more about the Myth of Arthur's hunt, or some Visit Details.