It exists, at ground level, as nothing at all; a field under tillage, sloping gently westward at the base of a hill range, unremarkable in every visible sense. What betrays it is the crop itself, which under the right conditions of drought and aerial light throws up a ghostly ring in the vegetation, the buried ditches below still influencing, after all this time, what grows and how.

The enclosure was identified from aerial photography, the technique by which so many of Ireland's vanished earthworks have re-emerged in recent decades. Cropmarks form when buried features, such as filled-in ditches or the remains of old walls, alter the moisture and nutrients available to plants above them, producing variations in colour and growth rate that become legible only from the air. In this case the site shows as a near-perfect circle, roughly 25 to 30 metres in diameter, defined by two fosses, the inner of which is wider and deeper than the outer. A foss, in this context, simply means a ditch, typically dug to define and defend a settlement or enclosure. The northern half of the ring appeared again in a separate aerial photograph taken in 1990, confirming what the earlier image had suggested. Roughly 120 metres to the south-southwest, another and larger circular enclosure is also visible as a cropmark, raising the possibility that this part of Garrannaguilly once held a cluster of related activity, though what precisely that activity was, and when, the surviving evidence does not say.