A ringfort, or rath, is a roughly circular enclosure defined by earthen banks and ditches, built during the early medieval period and used as a farmstead or place of domestic enclosure. This one at Croaghnacree has been levelled, absorbed into the tillage fields around it, leaving only a slight rise in the soil where the bank once stood. The strange persistence of such places is that even after the physical form is gone, the outline refuses to vanish entirely.

The 1842 Ordnance Survey six-inch map records the site not as an earthwork but as a ring of trees, suggesting the bank was still present at that point and being used, as was common, as a convenient boundary or windbreak. By the time the 1905 and 1937 editions were published, surveyors were marking it as a hachured circular enclosure, noting a diameter of approximately 35 metres, with a bank and an external fosse, that is, a ditch running around the outside of the main bank. Somewhere between those mappings and the present, the structure was flattened. Aerial photography has since done much of the work that ground-level inspection cannot. Photographs taken in July 1975 and July 1989 reveal the site as a cropmark, a phenomenon where buried features affect the growth of plants above them, making ditches and banks legible from the air in a way they are not from the ground. The 1975 image shows the cropmark of both the bank and the outer ditch; the 1989 photograph captures the fosse. Together they confirm the full plan of what was once a double-enclosed ringfort.