In a pasture field near Balline in County Limerick, a circular earthwork of around twenty metres in diameter has been reduced to little more than a ghost in the soil. It does not appear on any historic Ordnance Survey Ireland maps, it casts no shadow visible to Google Earth, and to a person walking the field today it would be effectively invisible. The only proof of its existence comes from the air, and even then the signal is faint.

The site first surfaced in the archaeological record through an oblique aerial photograph taken on 17 July 1968, part of the Cambridge University Collection of Aerial Photography archive, reference CUCAP BGK052. That image showed a trace of an enclosure or platform to the north of the ruins of Emlygrennan Church, which itself sits roughly fifty metres to the south. Aerial photography of this kind, taken at an angle rather than directly overhead, can reveal subtle changes in ground relief that are invisible at ground level. Decades later, orthophotographs taken by Ordnance Survey Ireland sometime between 2005 and 2012 showed what appears to be a circular cropmark at the same location, a cropmark being the phenomenon where buried features cause overlying crops or grass to grow differently, producing patterns legible from above. The diameter of approximately twenty metres is consistent with a modest enclosure of early medieval type, though the record stops short of assigning it a definite function or date. Compiled by Fiona Rooney and uploaded to the record in August 2021, the entry is careful to use the word "possible" throughout.

The ruins of Emlygrennan Church and its associated graveyard are the more accessible draw for anyone visiting the area, and the earthwork itself offers nothing to the naked eye at ground level. The field is in agricultural use, so access would require landowner permission. The cropmark, if it remains visible at all, would only be legible from the air or through the archived photographs themselves, which are held within the CUCAP collection. What the site does offer, in a less tangible sense, is a reminder of how much of the Irish landscape exists in a state between presence and absence, recorded in a handful of aerial frames taken on a summer afternoon more than half a century ago.