In a July 1989 aerial survey, the crop above the site betrayed what the soil conceals: the ghostly outline of a fosse, the defensive ditch that once defined a circular enclosure. Cropmarks of this kind appear when buried features affect how plants grow overhead, with ditches tending to produce lusher, taller crops due to retained moisture, while compacted foundations suppress growth. The result, briefly legible each summer depending on rainfall and crop type, is a shadow map of structures that have otherwise vanished from the landscape.

A fosse-defined circular enclosure of this scale is consistent with a ringfort, the most common archaeological monument type in Ireland, typically dating from the early medieval period, roughly the fifth to twelfth centuries. These were enclosed farmsteads rather than military fortifications, usually housing a single family and their livestock. At Ballygarrane, a possible entrance was identified to the south, though a field fence and a north-south laneway now cut across the western half of the site, obscuring whatever original form that edge may have taken. The enclosure does not sit in isolation: three further enclosures were recorded within approximately 150 metres of it, suggesting the area was once part of a broader settled landscape, its individual households or farmsteads clustered within reasonable proximity of one another, as was common practice across early medieval Ireland.