The site at Cornacreeve is the kind of place that registers as a slight irregularity in a field before it registers as anything else, yet its dimensions and construction mark it out as a deliberate, purposeful earthwork.

The enclosure is roughly subcircular, measuring approximately 29 metres northwest to southeast and 26 metres northeast to southwest, and it tilts gently downhill towards the southeast. What survives of its defining bank, most clearly visible at the south-southwest, has a base width of around 2.8 metres, rising just under half a metre on the interior and reaching 1.2 metres on the exterior. That asymmetry is typical of earthen ringforts, a class of enclosed settlement site built predominantly during the early medieval period in Ireland, roughly between the fifth and twelfth centuries. The single entrance, at the southeast, has a base width of 1.5 metres. Beyond the bank, an outer drain completes the enclosure's boundary. Such forts were generally the farmsteads of farming families rather than military fortifications, the raised bank serving to keep livestock in and to mark social as much as physical territory.