At the summit of Dunmurry Hill in County Kildare, rising to 796 feet above sea level, a low grassy bank traces a rough oval in the hillside turf. It is easy to walk past without a second glance, and easier still to mistake the concrete triangulation pillar at its north-western edge for the most significant thing present. In fact the pillar, which local livestock have adopted as a scratching post and churned the surrounding ground into a mess of poached earth, is almost certainly the least ancient feature on the hill. Beneath and around it lies something considerably older and considerably less legible.

The bank defines a small sub-circular enclosure, with internal diameters of roughly six metres north-east to south-west and five metres north-west to south-east. The outer dimensions are broader, closer to twenty-seven metres across at their widest, because the bank itself is unusually thick, ranging from about eight metres wide on the north-eastern side to over thirteen metres on the north-western side. It stands no more than half a metre above the interior and about a metre and a half above the ground outside. The whole structure sits within a hillfort, a larger defensive enclosure of the kind typically associated with the Iron Age in Ireland, which makes the enclosure inside it a monument within a monument. When the first edition of the Ordnance Survey six-inch map was published in 1838, surveyors marked the feature not as an enclosure but as a raised area or mound, and that older interpretation may be closer to the truth. The working theory now is that this may be the remains of a cairn, a burial mound of heaped stone, that has been partially robbed out over the centuries, its material taken for other uses until the original form became hard to read. A second possible cairn lies just eight metres to the north-east, suggesting the summit may once have carried more deliberate funerary or ceremonial significance than its current battered state implies.