The cropmark, spotted on aerial photographs from 2012, sits roughly 170 metres from the lakeshore, bisected by a later field boundary running roughly north to south. The clearer half survives on the western side of that boundary, where the rectangular shape can still be made out, along with what appears to be the cropmark of a trackway running from the eastern angle of the enclosure towards a medieval castle site some 220 metres away.

What makes the site genuinely difficult to interpret is the company it keeps. Within 220 metres lie the remains of a medieval church to the north, a possible mill site to the north-northeast, and the castle itself to the east, and the enclosure shares the same ENE-WSW alignment as the church. That clustering of monuments has led to the suggestion that this may be a moated grange or moated house, a type of enclosed medieval settlement often associated with ecclesiastical or manorial estates, typically defined by a rectangular earthwork with a surrounding ditch. There is also a documentary possibility. The Civil Survey of 1654 to 1656, a detailed land assessment carried out after the Cromwellian conquest of Ireland, recorded the townland of Castletowne as containing a castle situated close by the Shannon, a barbican, a slate house, a garden and orchard, a watermill, eight thatched tenements, and a parish church. The enclosure could plausibly correspond to either the slate house or the garden and orchard mentioned in that account, though no firm identification has been made. The date of the enclosure itself remains uncertain.