The one at Coolroe in County Wexford is more elusive than that. Its presence is registered not on the ground in any obvious way, but in the faint geometry of a cropmark, the kind of trace that only becomes legible when viewed from the air, when a buried ditch causes the soil moisture and vegetation above it to behave just slightly differently from everything around it.

What the aerial photographs reveal is a D-shaped enclosure, roughly thirty metres across on its longer axis and twenty metres on the shorter, defined by a single fosse, which is the term for the ditch that typically surrounds an early medieval enclosed settlement of this type. The rath, as this category of ringfort is sometimes called, sits on a fairly steep west-facing slope, with a north-south stream running about sixty metres to the west. The shape is not quite complete even in the aerial record; a section of road cuts across the north-eastern edge, truncating the enclosure and severing whatever continuity the fosse once had. By around 2013, a house had also been built just outside the south-western margin of the site, placing modern domestic life directly adjacent to what was once, in all likelihood, someone else's.