What gives it away is a ghostly circle, roughly 44 metres across, that shows up in aerial photography as a cropmark, a subtle difference in vegetation growth caused by buried features below the surface. Where a ditch once cut through the soil, moisture and nutrients behave differently, and crops above it grow at a slightly different rate or colour. From the air, in the right season and light, the outline of something ancient becomes legible again.

The circular form, defined by what appears to be a filled-in ditch, is consistent with a ringfort, the most common type of early medieval settlement in Ireland. Ringforts, which date broadly from around the fifth to the twelfth century, were typically enclosed farmsteads, their earthen banks and ditches marking out a family's living space and protecting livestock. Thousands survive across the Irish countryside in varying states of preservation, but a great many others were levelled by centuries of ploughing, leaving only these faint subsurface signatures. The Killoughy example was identified from Google Earth orthophotos taken in August 2022 and from aerial images captured in March 2009, neither of which had been previously connected to any mapped or recorded monument.