Low earthen banks, filled-in ditches, the ghost of a drystone wall, a faint depression running across a narrow neck of ground; none of it is dramatic, and none of it is conclusive, but taken together across six separate headlands it adds up to a pattern that is difficult to dismiss.

A promontory fort is exactly what it sounds like: a coastal or inland headland defended, usually by a bank and ditch across its landward approach, turning the natural cliff edges into walls. They are found throughout Ireland and along the Atlantic fringe of Europe, and their dates of construction span a wide range, though many in Ireland are associated with the Iron Age and early medieval periods. What makes this cluster at Ard Na Caithne unusual is the sheer repetition of the form across a short stretch of coastline, and the variability in what survives. The two northernmost headlands retain low earthen banks and traces of a levelled drystone wall at the neck. The broad rectangular headland beside them has the remnants of a wide bank and a faint fosse, the term for the ditch typically dug to reinforce such a barrier. The southernmost headland is defended by a slightly curving fosse that has since been filled in. The middle two are harder to read; recent agricultural banks complicate the picture, though vague traces of earlier activity are still visible beneath or behind them. A survey carried out in 2002 by Casey described the ensemble carefully and honestly, concluding that not enough survives to determine the exact nature of any individual site, but that all six headlands are candidates for promontory forts and warrant closer investigation.

The sites remain unexcavated and unverified, which is precisely what makes them interesting. They occupy a kind of liminal category in the archaeological record, present enough to be noticed, ambiguous enough to resist easy classification. Whether the headlands were ever formally connected, whether they represent a single organised defensive scheme or simply a coastline that different communities returned to independently over centuries, remains entirely open.