This is a rath, the Irish term for a ringfort, a type of enclosed farmstead that was the most common form of rural settlement in early medieval Ireland. Thousands survive across the island, yet each one preserves its own slightly different geometry, and this one at Ballinacrow is no exception.

The enclosure measures 34 metres in diameter, defined by an earthen bank that varies from two to three metres wide. The bank stands higher on the north-east side, reaching 1.8 metres internally, than on the south-west, where it drops to 1.2 metres; the external face levels off at around a metre. Outside the bank runs a fosse, a surrounding ditch, which widens considerably from roughly three metres at the north-east to five metres at the south-west, and drops to between half a metre and a metre in depth. The original entrance, three metres wide, faces south-west, a common orientation in Irish ringforts, possibly chosen to face away from prevailing weather or towards the most productive land. A separate modern gap has been cut into the south-east of the bank at some later point. Inside the enclosure, two rectangular structures survive as low narrow banks: one measuring 16.8 by 6.5 metres, the other 11 by 4 metres. These are noted as possibly not contemporary with the main enclosure, which raises quietly interesting questions about the site's long use and reuse over time. Whether these interior features represent later agricultural buildings, subdivisions, or something else entirely remains unresolved.