It is large enough, and positioned well enough, to have once been a serious piece of defensive real estate. But the thing that makes it quietly odd is this: the earthwork that originally sealed off the promontory, a great curving bank thrown across the isthmus to turn the headland into an enclosed place, has all but vanished at ground level. Walk out along it today and you would likely see nothing unusual. Look at it from the air, and the ghost of the bank re-emerges, tracing its arc across the neck of land with reasonable clarity.

A promontory fort of this kind works by exploiting natural geography: the sea defends three sides, and a bank, ditch, or wall across the landward approach completes the enclosure. They are found all around the Irish coastline, and their dates vary considerably, though many belong to the Iron Age. At Cill Ghallagáin, what survives of that defensive bank has been disturbed by a road and a modern stone wall cutting across the isthmus, which accounts for much of its disappearance at surface level. Inside the enclosed headland there is fertile pasture, suggesting that whoever held this place had both a defensible position and workable land within their perimeter. The site was noted by the antiquarian T. J. Westropp, who catalogued many such sites along the Irish coast, though he ultimately left this one off his final published list in 1912, which may partly explain why it has attracted less attention than comparable sites elsewhere.

The bank, though indistinct underfoot, is worth looking for at the isthmus where the road crosses onto the headland. The combination of disturbed earthwork, open pasture, and wide views across Broadhaven gives the place a slightly unresolved quality, like something half-remembered. Its most legible form exists, for now, in aerial photographs rather than in the landscape itself.