An aerial photograph taken in July of that year captured a circular cropmark, roughly forty metres across, betraying the buried outline of an ancient enclosure. The cropmark formed because the filled-in ditch, or fosse, that once ringed the site retains moisture differently from the undisturbed soil around it, causing the plants above it to grow at a slightly different rate. The result, invisible at ground level, becomes legible from the air as a ghostly ring pressed into the grain.

What makes the Ballygrace site particularly interesting is not just the enclosure itself but two parallel linear cropmarks that approach it from the south-east, suggestive of a former trackway or field boundary that once connected to the site in a purposeful way. Circular enclosures of this kind, when not otherwise classifiable as ringforts, a ringfort being a farmstead enclosed by an earthen bank and ditch common across early medieval Ireland, are often interpreted as settlement or ritual sites of broadly similar date, though without excavation it is impossible to say more. The landscape around Ballygrace adds context: two ringforts lie within approximately a hundred and eighty metres, one to the south-west and one to the south-east, suggesting this was a settled and organised piece of ground during the early medieval period, with multiple enclosures in relatively close proximity to one another.