This one in Ballyshane, County Offaly, offers nothing so obliging. Walk across the ground and you would notice nothing at all; the enclosure is entirely invisible at surface level, leaving no earthwork, no ridge, no shadow in the grass. Its existence is known only because a set of Air Corps aerial photographs, referenced as 757/8, caught what appears to be a semicircular arc traced into the landscape from above, the kind of cropmark or soil variation that only becomes legible when seen from altitude.

Enclosures of this type are a reasonably common feature of the Irish countryside, typically circular or roughly circular boundaries that once defined a farmstead, a ritual space, or a place of habitation, often dating from the early medieval period though sometimes considerably older. The fact that this one survives only as a partial arc, described cautiously as a "possible enclosure", means its purpose and date remain genuinely uncertain. Aerial photography has been one of the most productive tools for locating such features in Ireland, revealing the outlines of structures that centuries of ploughing, drainage, and settlement have otherwise erased entirely. What the Air Corps photographs captured at Ballyshane is, in that sense, a fairly typical discovery made by an atypical method: the landscape holding its secrets until the angle of light or the stress of a dry summer briefly gives them away.