That sentence contains the full extent of what can be said with confidence. It is an unusual situation for a prehistoric structure, and yet it is not entirely uncommon in Irish archaeology, where nineteenth-century records describe things that later generations have struggled to put their hands on.

The source of the uncertainty is a reference in the Ordnance Survey Letters of 1837, those remarkable documents compiled as part of the great mapping project that traversed the country townland by townland. The letters note the presence of a cromleac, the older Irish term for what would now generally be called a portal tomb or dolmen, a type of Neolithic monument in which large upright stones support a massive capstone, creating a chamber that once served as a burial site. The dimensions recorded are specific enough to suggest a substantial structure: a length of 4.27 metres and a width of 2.44 metres. The site falls within the barony of Rathdown, on the southern fringe of County Dublin. Beyond this, and the reference cited by Herity in 2001 to the same OS record, the paper trail runs cold.

For anyone curious enough to visit the area around Newtown Hill, the honest answer is that there is no confirmed location to aim for. The monument has not been precisely located by subsequent survey or excavation, and it may have been disturbed, dismantled, or simply obscured over the intervening two centuries. What the area does offer is the quiet experience of walking ground where something almost certainly once stood, in a county not generally associated with megalithic remains. The Rathdown baronial landscape is worth attention in its own right, and anyone with a particular interest in the archaeology of Dublin's upland fringes might find the OS Letters themselves, held in accessible archives, a more rewarding starting point than any map.