This one is remarkable for what does not. On a headland near Clashmelcon in north County Kerry, a promontory fort once occupied a coastal spur known as Dooneen, and by the time anyone thought to record it properly, it had already nearly vanished. Today, nothing at all remains on the surface.

A promontory fort is one of the more elemental forms of ancient enclosure: a naturally defended spit or headland made more secure by throwing up a bank and fosse, a ditch, across the landward approach, letting the sea cliffs do the rest of the defensive work. At Dooneen, the barrier took the form of a crescent-shaped stone bank, roughly three metres wide and just under a metre high, fronted by a shallow fosse about the same depth. A narrow causeway, one metre across, crossed the fosse and rampart to give access. When the antiquarian Thomas Johnson Westropp visited and recorded the site in 1910, noting its dimensions and form in his published survey, he observed that the fort was already very much levelled. Even that diminished state is now gone; no surface trace of the bank, the fosse, or the causeway remains. The site sits just south of a structure recorded separately as Brown's Castle, which at least retains some visible presence, unlike its vanished neighbour.

What makes Dooneen quietly interesting is the gap it represents between the landscape as recorded and the landscape as it now exists. Westropp caught it at the last possible moment, and his 1910 description is effectively the only material evidence that the fort existed at all. The name Dooneen, a diminutive of the Irish word dún meaning fort or fortified place, suggests the headland was identified locally by its defensive character long before any formal survey took notice of it.