What marks it out is its completeness as a form: a near-perfect circle, measuring thirty-nine metres across in both directions, defined by an earthen bank still standing to around a metre in height, with a shallow external fosse, or ditch, running around its outer edge. A possible entrance gap on the eastern side hints at how the enclosure was once approached, and somewhere in its southern portion there may be a souterrain, an underground passage or chamber of the kind commonly associated with early medieval settlement in Ireland, used variously for storage, refuge, or both.

Ringforts of this type, known in Irish as raths, were the most common form of rural settlement in early medieval Ireland, typically from around the sixth to the twelfth century. Most were farmsteads enclosed by one or more earthen banks, offering a degree of protection for a household and its livestock. The example at Drumnashinnagh was recorded in a 1994 archaeological survey of the Ballinrobe district compiled by D. Lavelle, which covered the wider area around Lough Mask and Lough Carra. That landscape, shaped by post-glacial lake systems and low drumlin ridges, contains a considerable density of such monuments, many of them sitting unobtrusively in fields that have been farmed continuously since long after these enclosures fell out of use.