Others exist only as shadows in a field, legible solely from the air on the right summer morning. At Subulter in north County Cork, a circular enclosure of around thirty metres in diameter falls into the second category. What survives at ground level is essentially nothing; what survives in the photographic record is a cropmark, the faint but telling outline of a fosse, which is the ditch that would originally have encircled the enclosure, showing up as a difference in crop colour and growth where buried soil disturbance affects the plants above it. A field fence has clipped the northeastern arc of the circle, so even the cropmark itself is incomplete, truncated before it can close.

The enclosure came to wider attention through an aerial photograph taken in July 1989 as part of the Cork Archaeological Survey Aerial Photography programme. Cropmarks of this kind are most visible in dry summers, when stressed crops over shallower, disturbed soils yellow faster than those rooted in deeper, undisturbed ground, and the buried geometry of old ditches and banks reads briefly as colour contrast from above. The site sits within a wider field system, and a second circular enclosure lies roughly a hundred metres to the south-south-east, suggesting that this part of north Cork was organised and occupied in ways that left their imprint well below the current surface. Circular enclosures of this general type in Ireland often date to the early medieval period, though without excavation the date of this particular example remains unknown.