This is a rath, the Irish term for a ringfort, a class of monument that once numbered in the tens of thousands across Ireland and functioned as a defended farmstead during the early medieval period, roughly between the fifth and twelfth centuries. Most people pass such earthworks without recognising them for what they are, reading them as nothing more than a slight rise in a field.

The enclosure at Ballycumber measures roughly 30.5 metres across on its northwest to southeast axis and 37.5 metres on its northeast to southwest axis, making it a reasonably substantial example of its type. Its boundary is formed by an earth and stone bank with a drystone facing, the stones carefully laid without mortar in the tradition common across early Irish construction. The bank itself runs about 2.8 metres wide, and while it stands only modestly above the interior ground level, between 0.4 and 1.3 metres on the inside, the external face rises to between 0.7 and 1.4 metres. Beyond the bank runs a fosse, a defensive ditch about 3 metres wide and up to 1.3 metres deep, most legible now along the northern arc where it remains clearly defined. One entrance, positioned at the northwest, appears to be original and retains its form with some integrity. Two further gaps in the bank, at the southeast and east-southeast, are likely modern breaks rather than ancient thresholds. There are no surviving internal features, meaning whatever structures once occupied the enclosed space, whether timber buildings, hearths, or storage pits, have left no visible trace above ground.