Levelled by centuries of ploughing, it survives only as a cropmark, that quiet phenomenon where buried earthworks affect the growth of crops above them, causing slight but legible differences in colour and height that become visible from the air. It is one of those places that requires an aerial photograph to be seen at all.

The site was once a rath, the Irish term for a ringfort, typically a circular enclosed homestead of the early medieval period, defended by an earthen bank and an outer ditch called a fosse. At Rathnacarton, the enclosure measured approximately thirty metres in diameter. It was mapped as a hachured circle on Ordnance Survey six-inch sheets in 1842, again in 1905, and once more in 1935, which means that cartographers were still recording it as a visible feature well into the twentieth century. Somewhere between those surveys and the present, the bank was finally removed entirely. An aerial photograph, catalogued under the Geological Survey of Ireland Air Photo collection as reference R523, shows the circular outline of both the bank and the external fosse preserved as cropmarks in the field below.