Standing on the ground, you would see nothing: no earthwork, no raised bank, no depression in the soil. The site at Ballynaslee is known solely because a camera mounted in an aircraft once caught the light at the right angle, and the ghost of a rectangular outline appeared in the crop or grass below.

Aerial photography has long been one of archaeology's quieter tools. Buried or levelled features can alter how vegetation grows above them, drawing faint lines across a field that are invisible to anyone walking through it but legible from height. In this case, the photograph, catalogued under the Cambridge University Collection of Aerial Photography reference AJQ 52, revealed a roughly rectangular enclosure measuring approximately 25 metres east to west and 30 metres north to south. It sits on slightly rising ground just above the flood plain of the River Nore, in the kind of gentle valley-floor position that was favoured for settlement and farming across many periods of Irish prehistory and early history. Without excavation, it is not possible to say what the enclosure was for, who built it, or when, and none of that has been attempted here.

For a visitor, there is genuinely nothing to see at ground level. The interest lies almost entirely in the idea of the place: a structure substantial enough to have left a trace readable from the air, yet so thoroughly returned to the earth that the field gives no hint of it at all.