Cup-marks, the most common form of prehistoric rock art found in Ireland, are shallow, roughly circular depressions pecked into stone surfaces, their precise purpose still debated by archaeologists. That such carvings should survive beneath what is now one of the busiest road corridors in the country gives them a particular, quiet strangeness.

Three small boulders bearing cup-marks were uncovered during archaeological investigations carried out along the route of the South-Eastern Motorway, recorded under the site reference DU026-146/147. The finds are documented in the 2002 and 2004 reports of Clinton, and were examined in detail by Dr Muiris O'Sullivan, whose description of the most closely studied of the three, designated Rock A, is recorded in a substantial excavation report compiled by T. Breen in 2012 on behalf of Dún Laoghaire-Rathdown County Council. Rock A is a slightly rounded granite boulder with a convex carved face measuring 0.61 metres by 0.38 metres. At least 24 cup-marks are visible across that surface, ranging from approximately 4 centimetres across down to roughly half that diameter. Despite the variation in size, O'Sullivan observed that the cup-marks form a coherent group, consistent in their general arrangement, individual form, and carving technique, suggesting a single purposeful act of creation rather than casual or accidental marking.

Because these boulders were recovered during a road scheme rather than found in situ in the open landscape, they are not accessible to visitors in the conventional sense. They belong to the world of the excavation archive and the specialist report rather than the signposted site. Anyone with a serious interest in the material would do well to consult the Breen 2012 report directly, which includes a drawn record of the rock art at Figure 8.3.1. The National Monuments Service Sites and Monuments Record holds the formal registration for the site. For those content to stand somewhere in the vicinity and contemplate the fact, the Carrickmines area around the M50 corridor marks the approximate location where, beneath the engineering of a modern road, somebody once spent considerable time pressing cup-marks into granite, for reasons that remain entirely their own.