The enclosure at Crosscoolharbour is roughly thirty metres across, a modest but deliberate ring on a south-east-facing slope about three hundred metres north of the River Liffey. It is the kind of feature that disappears entirely at ground level, swallowed by plantation conifers, yet resolves itself clearly when seen from the air.

Circular enclosures of this type are scattered across Ireland and can represent quite different things depending on their age and construction. Some are the remains of ringforts, the enclosed farmsteads that were the dominant settlement form of early medieval Ireland, typically defined by an earthen bank and external ditch. Others may be of prehistoric origin, associated with burial or ritual rather than habitation. The Wicklow uplands contain examples of both, and without excavation it is rarely possible to say with confidence which category a given site belongs to. What is clear here is the geometry: a regular, intentional circle, sitting on a hillside that would have offered a reasonable outlook toward the river valley below.