This is Lissadooneen, a name that the Ordnance Survey mapped faithfully in both its 1840-41 and 1914-15 editions, rendering the Irish Lios an Dúinín as something like "ringfort of the little fortification", a name that folds the site's own character into itself. What makes it quietly arresting is not just its position at the geographic limit of its type on this coastline, but the company it keeps: roughly 7.5 metres from the fortification lies the burial place of a ship's crew, and a standing stone sits to the south-east, lending the headland the layered quality of a place that different eras found meaningful for different reasons.

A promontory fort works by letting the sea do part of the defensive work, using a cliff-edged peninsula as a natural enclosure and cutting earthworks across the neck of land to seal it off. At Lissadooneen, those earthworks are substantial. The curved fosse, a defensive ditch, runs 30 metres through with a causeway, 5.1 metres long and 2.5 metres wide, providing the only crossing point. The fosse itself is deep; dropping 2.8 metres below the outer bank and as much as 6 metres below the inner one at certain sections. That inner bank rises steeply from the ditch floor to stand 3.4 metres above the enclosed interior, and measures 10 metres in width at its base. The outer bank is lower and broader, ranging between 0.7 and 1.2 metres wide with an external height of around 1 metre. The enclosed interior is wedge-shaped, approximately 50 metres long and 33.2 metres wide. Perhaps most telling is the condition of the fosse: it remains largely unfilled, which researchers have taken as a possible sign that the earthworks were actively maintained well into later periods, long after the original context of the fort had shifted or been forgotten.