The northern half is the portion that holds its shape, describing a near-circular enclosure roughly 38 metres across, its perimeter marked by an earthen bank about five metres wide.

A rath, as ringforts of this earthen type are known, was the standard farmstead of early medieval Ireland, typically occupied between the sixth and tenth centuries. A family and their livestock would have lived within the enclosure, protected by the raised bank and, usually, an external ditch called a fosse. This example at Barnbawn sits on a pronounced north-east-facing slope in County Wicklow, and the bank itself still stands to an external height of between 0.8 and 1.3 metres, slightly higher on the outer face than the inner, which reaches only 0.7 metres. There is a possible entrance gap, about three metres wide, at the north-north-west. What is notably absent here is any sign of the fosse that would typically ring such an enclosure, and no internal features have been identified either, leaving the site as a largely unelaborated outline of what was once a functioning domestic space.