The northern portion of the enclosure at Ballynamona was quarried away at some point, leaving what survives as a kind of cropped arc rather than the complete circuit it once formed. What remains is an almost circular rath, measuring roughly 28 metres east to west and 27 metres north to south, set on a south-facing slope in grassland. A rath is an early medieval enclosed farmstead, typically defined by one or more earthen banks with a ditch between them; this one retains two banks and the intervening fosse, the fosse being the ditch dug to create the bank material, in reasonably legible condition along the southern and western arcs.

The monument is complicated further by a field wall that cuts across it at the north-north-east and south-east, and to the east of those points the enclosing elements have been reduced to very little. Inside, in the south-western section, a low bank running roughly north-west to south-east may represent an internal division of the original enclosed space, the kind of feature that sometimes separated a domestic area from a livestock pen or storage area. Taken together, the quarrying, the intrusive field wall, and the differential survival give the site an almost stratigraphic quality, several different periods of use and damage legible at once in the same modest patch of ground.