It cannot be seen from the road, or even on foot in any obvious way. It shows up only from above, as a cropmark, where the buried remains of an ancient circular enclosure roughly thirty metres in diameter cause the grass or grain growing over it to ripen or dry at a slightly different rate than the surrounding soil. The result, visible in aerial imagery, is a ghostly ring pressed into the landscape, a signature left by a structure that has long since vanished at ground level.

Cropmarks form when buried features, walls, ditches, or pits, affect the depth and moisture of the soil above them. Filled ditches tend to retain more water and nutrients, producing lusher, greener growth; buried walls or compacted surfaces do the opposite, creating paler, drier strips. A circular enclosure of this kind in an Irish context could represent any number of things: a ringfort, which was typically a farmstead enclosed by an earthen bank and ditch during the early medieval period; or something older still. Without excavation, the date and function of the Garryduff feature remain open questions. What is known is that a circular cropmark approximately thirty metres across was identified in Google Earth aerial photography captured on 28 June 2018.