Others exist only as faint signatures in the soil, legible solely from the air under the right conditions. The enclosure at Poulnareagha, in north County Cork, belongs firmly to the second category. What survives above ground amounts to nothing the eye would readily catch; the evidence lies in a cropmark, the phenomenon whereby buried features such as ditches or walls cause overlying crops to grow at slightly different rates, producing ghostly outlines visible in aerial photographs that would be invisible to someone walking the same field.

The cropmark in question was captured in July 1989, when aerial survey recorded an arc of fosse, a ditch that would originally have defined the boundary of an enclosure, running from north-north-west to south-south-east along the east-north-east side of an existing field fence. From that partial arc, the enclosure has been interpreted as roughly circular, with a diameter of approximately forty metres. Circular enclosures of this kind are a familiar feature of the Irish landscape and are frequently associated with early medieval settlement, though without excavation it is impossible to assign a firm date or function to this particular example. What makes the Poulnareagha site quietly interesting beyond its own modest footprint is its relationship to a neighbouring feature: a rectangular enclosure lies roughly a hundred metres to the north. The proximity of a circular and a rectangular enclosure is not unusual in itself, but the pairing invites questions about sequence and connection that the available evidence cannot yet answer.