That is the essential logic of a promontory fort, a form of defended enclosure found all around the Irish coast, where Iron Age communities recognised that the sea itself could do most of the defensive work. A deep ditch or rampart thrown across the neck of a coastal spur left three sides protected by cliff and water, requiring only that single barrier to complete the enclosure. The result is a monument type that tends to survive well precisely because the terrain that made it useful also made it difficult to farm or build over.

Castlehaven, the inlet south of Skibbereen, has a coastline of considerable geological drama, its headlands bitten into irregular shapes by the Atlantic. Promontory forts in this part of Cork are relatively common, reflecting how densely the Iron Age population worked with the natural geography of the Mizen and Sheep's Head peninsulas and the broader stretch of coastline running toward Mizen Head. The specific earthworks at this site, the precise dimensions of any surviving bank or fosse, and the degree to which the defences remain legible on the ground, are details that await fuller documentation.

The site sits within a landscape where coastal archaeology repays patient attention. Visitors walking headlands in this part of Cork will sometimes find the outline of a cutting across a promontory neck barely distinguishable from a natural terrace, weathered and grassed over, but present nonetheless once the eye adjusts to what it is looking for.