Not obscured by trees or fencing, not buried beneath a later building, but simply gone from the surface of the ground, leaving no trace visible to the naked eye. What survives exists only in the archaeological record and, crucially, in the cartographic memory of the 1843 Ordnance Survey six-inch map, which recorded a circular ring of stones roughly thirty metres in internal diameter, complete with a central division and a hut site in the eastern half of the enclosure. The site carries the reference DU025-043002-, a dry string of characters that is, in practice, all that remains above ground.

The structure belongs to a category known as a cashel, a term used in Irish archaeology for a ringfort built from stone rather than earthen banks. Ringforts, which date broadly from the early medieval period, were enclosed farmsteads, the stone or earthen boundary serving to define a household's space and protect livestock. Cashels tend to survive better in the rocky west of Ireland, where stone was plentiful and the land never quite worth ploughing flat. On the Dublin uplands the record is patchier. The site at Ballybrack was documented and compiled by archaeologists Geraldine Stout and Padraig Clancy, with a revised entry uploaded in July 2018, suggesting the record has been revisited and checked against available sources rather than simply inherited uncritically from older surveys.

The southern-facing slopes of Two Rock Mountain are accessible from several points along the Dublin Mountains foothills, though this particular site offers no marker, no interpretive panel, and, as the record plainly states, nothing visible at ground level. A visitor who made their way there would be relying entirely on map coordinates and an understanding that absence is itself a kind of evidence. The 1843 OS map remains the most useful reference point, showing the outline of the enclosure at a moment when it was presumably still legible as surface stonework, even if only faintly so. What has happened to those stones in the intervening 180 years, whether cleared for grazing, robbed for field walls, or simply pressed beneath centuries of turf and vegetation, the notes do not say.