The evidence for this site exists almost entirely from the air, where the outline of a circular enclosure, roughly 46 metres across, reveals itself as a cropmark, the kind of subtle discolouration in growing crops or parched grass that betrays buried features to anyone looking down from above at the right moment.

Cropmarks form when buried ditches or walls affect the soil's ability to retain moisture. Over a filled-in fosse, a ditch typically dug to define and defend an enclosure, crops tend to grow taller and greener; over buried stone or compacted ground, they stay shorter and yellower. On 16 July 1989, an aerial photograph catalogued as GB90.AA.08 captured exactly this kind of signature at Castlegrace, tracing the ghost of a circular enclosure defined by a fosse. Circular enclosures of this type are common across Ireland and are broadly associated with the early medieval period, though without excavation it is difficult to say more about the function or date of any individual example. They range from high-status ringforts, which served as enclosed farmsteads, to ecclesiastical enclosures surrounding early churches. At around 46 metres in diameter, this one falls within the range typical of a modest ringfort, though that remains an inference rather than a confirmed fact.