Near Kilmacahill in County Kilkenny, the arc of what may be an ancient enclosure exists only as a cropmark, a ghostly outline that emerges in aerial photography when the soil's buried past causes growing crops above it to ripen or wither at slightly different rates than the surrounding field. The site is currently under tillage, and a river runs along its southern side on a northwest to southeast course, a detail that would have made the location attractive to early settlers who needed reliable water access.

The enclosure was first identified from an aerial photograph taken on 18 July 1970 as part of the Cambridge University Collection of Aerial Photography, a systematic effort to document the Irish landscape from the air that captured many sites otherwise invisible from the ground. Cropmarks of this kind often indicate the buried remains of a circular or sub-circular enclosure, the type of enclosed settlement found throughout Ireland from the prehistoric period into the early medieval era. What makes the Kilmacahill site particularly interesting is that it does not sit in isolation. Roughly 120 metres to the east, aerial evidence points to a second possible enclosure, raising the question of whether these represent two phases of activity on the same spot, or perhaps a pair of related settlements occupying neighbouring ground along the same riverbank.