This one in Ballynasculloge, on the upland pastures of County Wicklow, offers nothing of the sort. Walk the ground and you will see only rough grazing land on a gentle north-facing slope, with no visible trace of anything beneath your feet. The enclosure exists, as far as any casual observer is concerned, only from the air.

What aerial photography reveals is a cropmark, a ghostly outline roughly 25 metres by 20 metres in extent. Cropmarks form when buried structures affect the soil above them, causing whatever grows at the surface to respond differently, sometimes more lushly over a ditch, sometimes more sparsely over a buried wall. These subtle variations, invisible at eye level, can become legible from altitude, particularly in dry summers when differential growth is most pronounced. The enclosure at Ballynasculloge falls into this category entirely. Its shape, a modest roughly rectangular form, is known only through aerial survey, and beyond its dimensions and its position on that quiet upland slope, the site keeps its history to itself.