What survives is a cropmark, the kind of ghostly outline that appears in aerial photographs when buried features cause overlying crops to grow at slightly different rates, revealing shapes otherwise invisible to anyone walking the field. In this case, the cropmark traces a bivallate ringfort, meaning a roughly circular enclosure defined by two concentric banks and ditches rather than one, sitting on a gentle west-facing slope.

Ringforts, also known as raths, were the most common form of rural settlement in early medieval Ireland, typically serving as enclosed farmsteads between roughly the fifth and twelfth centuries. The Garryduff example is modest in scale: the interior measures approximately 25 metres in diameter, with the outer enclosure extending to around 38 metres across. The double-ring arrangement, while not rare, suggests a degree of status or a need for additional security above the most basic farmstead. The site was identified through aerial photography, and its outline remained legible enough to be confirmed again in digital aerial photographs taken in 2006, decades after it first appeared in the record.