A cashel is a stone-walled ringfort, the drystone equivalent of the more familiar earthen enclosures found across Ireland, and this one, named Caherduff on the first Ordnance Survey maps of 1842, was built with a care that is still legible in its surviving masonry. The position was clearly chosen with purpose: the terrace edge faces north, the views run west and across the bay, and the wall that once enclosed the interior was engineered to last, with a controlled inward lean, known as batter, of one inch for every twelve inches of height.

When the antiquarian Thomas Johnson Westropp visited and recorded the site in 1905, he found the wall standing over ten feet high in places, with a thickness of nine to ten feet and two distinct stone faces packed with a large rubble fill between them. He noted a narrow internal terrace running around the inside of the wall, perhaps a walkway or a structural feature, and described the interior as slightly hollow and irregular, with large rocks scattered about and an oblong depression that suggested the bedrock had at some point been deliberately quarried. His published sketch of the monument, made during that visit, remains one of the clearest records of how the cashel appeared before further deterioration set in. The Cassini edition of the six-inch map, produced in 1915, still named it Caherduff, indicating the name was stable in local use for at least the better part of a century.

Today the cashel is most convincingly preserved along its southern and south-western arc, where the outer wall face still stands between 2.4 and 2.6 metres high. The northern face has fared less well; a later field wall was at some point incorporated directly into the cashel wall along that stretch, from the north-west around to the north-east, which both damaged the original fabric and complicates any reading of the structure there. The interior is overgrown and uneven, scattered with displaced stone blocks that may be the collapsed remains of internal structures, small houses or hut sites perhaps, though the density of fallen material means anything beneath remains effectively hidden.