Dense with trees and bushes, it reads from the shore as little more than a circular thicket, roughly fourteen metres across internally. What it actually is, though, is a crannog, one of the artificial or partly artificial islands that people across Ireland and Scotland built on lakes and rivers from the Bronze Age onwards, well into the early medieval period, as defensible homesteads. The water did the work that walls might otherwise do.

Crannogs are not rare in Irish lakes, but they are easily overlooked, precisely because they tend to look like nothing in particular. Time and vegetation do an efficient job of disguising the human effort underneath. The mound at Cappagh sits in Cavan, a county whose landscape of small drumlins and loughs made it well suited to this kind of settlement, where a body of water offered both a natural barrier and a reliable resource. The interior diameter of around fourteen metres is consistent with a modest enclosed living space, enough for a family and perhaps some livestock, ringed by whatever palisade or revetment the original builders put in place.