The Coflein record says that “A single massive rampart crowns a visually distinctive, flat-topped hill, creating a roughly triangular enclosure, about 300m east-west by 180m.” Visually distinctive eh, catching the eye of those folk and their stories. Marie Trevelyan tells us:
Merlin’s Cave is in Merlin’s Hill, above the secluded village of Abergwilli, near Carmarthen. Old stories state that Merlin is held there in bonds of enchantment by Nimue-Vivien, and it was firmly believed in the eighteenth century that the celebrated magician could be heard at certain seasons of the year bewailing his folly in allowing a woman to learn his secret spell.
Folk stories and Folk lore of Wales (1909).