It encloses about 80 acres within its defences, yet those defences are, by any measure, modest: a bank and external fosse running north to south for some 500 metres across the landward side, the inner bank no more than two metres above the base of the fosse, the outer bank barely half a metre high and largely indistinguishable from the ordinary field boundaries around it. For a promontory fort, which typically uses earthen or stone ramparts to seal off a headland from the mainland and let the sea cliffs do the rest of the work, the disproportion here is striking. The sheer scale of what is enclosed makes the earthworks feel almost incidental, as though the headland itself was always the point rather than anything built upon it.

That sense of the place mattering in ways beyond simple defence is not a new observation. The antiquarian T. J. Westropp, writing in 1910, suggested that An Dún Mór may have functioned as a ritual site, a sanctuary associated with the goddess Duibhne, the figure from whom the wider Corca Dhuibhne region takes its name. The archaeology does little to dispel that idea. Standing at the summit is an ogham stone, the early medieval script of incised strokes along a central line, two metres tall and carved with the inscription ERC MAQI MAQI-ERCIAS (MU) DOVINI(A), meaning roughly "Erc, son of the son of Ercias, of the Dovinia." John Windele found it lying flat when he visited in 1838; by 1839 it had been re-erected, apparently at the initiative of a Chatterton who visited shortly afterwards. Parts of the inscription, particularly the second-to-last word and the final letter, have since become difficult or impossible to read. Elsewhere on the headland, R. A. S. Macalister was told in 1899 of a souterrain, an underground stone-lined passage of the kind often associated with early Christian or early medieval settlement, which had reportedly contained bones and a cross-inscribed stone. Two inhumed burials were also found near the southern end of the defences, adding to the impression of a place that accumulated significance across several centuries.