The enclosure here exists not as a visible earthwork but as a cropmark, a ghost pressed into the soil that only becomes legible from the air. In a July 1989 aerial photograph, the fosse, the defensive ditch that once ringed a circular enclosure roughly 25 metres across, showed up as a dark or lighter band in the growing crop above it, where buried features alter how plants take up moisture and nutrients. The possible entrance appears to have faced east, which is a common orientation for enclosures of this type in Ireland.

What makes the field at Ballylegan particularly interesting is the density of related features within a small area. A second circular enclosure sits roughly 50 metres to the south-east, and a ring-ditch, a circular ditched feature that may mark the site of a ploughed-out burial mound or a former enclosure of a different kind, lies about 140 metres to the east-north-east, all within the same field. The clustering of such features is not unusual in the Irish landscape; enclosed settlements, often associated with the early medieval period, sometimes occur in loose groupings that suggest long-term use of a particular stretch of land. But finding three distinct cropmark features in such close proximity points to a landscape that was once considerably more occupied and organised than its current agricultural plainness suggests.