The site at Ballynacor is a rath, the Irish term for a ringfort, which was the standard form of rural settlement across Ireland roughly between the fifth and twelfth centuries. Most were farmsteads, enclosed by one or more earthen banks to protect livestock and signal status. This one has two concentric banks with an intervening fosse, the ditch between them, and the whole oval enclosure measures approximately twenty metres north to south and twenty-six metres east to west.

The layout still reads clearly on the ground. There is a proper entrance gap, around three and a half metres wide, at the east-northeast, and a causeway of compacted earth just under two metres across carries the approach over the fosse, which would once have made the interior genuinely difficult to rush. The fosse and outer bank have been partly levelled on the eastern side where a field fence cuts across on a north-south line, a common enough fate for earthworks that sat in the way of agricultural improvement. The interior rises slightly towards the centre, and several large tree stumps suggest it was wooded at some relatively recent point, though the trees are now gone. What remains is the ridge itself, the banks, and the long sightlines outward in every direction, which presumably mattered just as much to whoever built this place as the enclosure itself.