The site is easy to overlook. It does not appear on any edition of the Ordnance Survey maps, and as recently as 1995 local tradition held that a promontory fort had once stood here, with no visible trace remaining to support the claim. The story might have ended there, a rumour attached to a headland, had a later survey not looked more carefully at the ground itself.

A promontory fort is one of the oldest and most elemental forms of coastal enclosure in Ireland, using the natural drama of a cliff-bound headland in place of a full circuit of walls, with a constructed barrier thrown across the neck of land where the sea cannot defend. At Dreenagh, that barrier is still faintly legible. A fosse, which is a defensive ditch, roughly 4.5 metres wide, cuts across the broad neck of the headland, accompanied by earthen banks now worn down to a scarp less than a metre high. A causeway, three metres wide, crosses the fosse about nineteen metres from the eastern edge, suggesting a deliberate original entrance rather than later erosion. The enclosed interior stretches approximately 35 metres wide by 38 metres long, flat and featureless, covered in coarse pasture, with a perimeter bank still traceable along the western cliff edge and the ground sloping gradually to the northern point. Casey, writing in 2002, concluded that this was in all likelihood the site that earlier researchers had noted but failed to locate, its presence concealed not by dramatic collapse but by slow, quiet reduction.

What makes the place quietly odd is precisely that gap between absence and presence. One generation of researchers found nothing and recorded the memory of something; the next found the earthworks and matched them to the memory. The fort itself, whatever it once enclosed and whoever built it, has left almost nothing to read. The fosse, the causeway, the faint bank along the cliff: these are the punctuation marks of a text that has otherwise been grazed away.