What survives here is a rath, the Irish term for a ringfort, the most common type of early medieval settlement in Ireland. Thousands were built across the country between roughly the fifth and twelfth centuries, typically as enclosed farmsteads for a single family and their livestock. Most people driving through the Irish countryside will have passed dozens without registering them.

The Cartronmore example is modest but coherent in its remains. The roughly circular enclosed area measures approximately twenty-two metres in diameter, defined by a low bank of earth and stone about three metres wide, which still stands to an internal height of around half a metre. At the outer base of this bank runs a fosse, the shallow ditch dug when the bank material was first excavated, here roughly two metres wide and forty centimetres deep. On the south-south-west to west-south-west side, the bank and fosse disappear entirely, replaced instead by a natural or modified scarp that drops about a metre on the outside face. Whether that absence reflects deliberate construction, later erosion, or some combination of both is not clear from what survives. The original entrance, which in many ringforts appears as a deliberate gap or causeway across the fosse, is no longer recognisable here.