It shows up as a cropmark, a phenomenon where buried ditches or banks cause the vegetation above them to grow at a slightly different rate or colour than the surrounding soil, revealing the ghost of an old enclosure in shades of yellow and green depending on the season. In this case, the circle measures approximately fifty metres in diameter, and it has gone largely unnoticed in the published record.

The feature was identified from a Google Earth orthoimage captured on 24 June 2018 and confirmed on Apple Maps. The record was compiled by Caimin O'Brien, working from details supplied by Jean-Charles Caillère, and uploaded to the database in November 2021. Beyond those bare facts, the site's age and original function remain unattributed. Circular enclosures of this kind in Ireland are frequently associated with early medieval settlement, the class of monument commonly called a ringfort, though without ground survey or excavation it would be premature to say so definitively here. What the cropmark does confirm is that something substantial was deliberately constructed at this spot, almost certainly involving a large circular ditch, and that it has survived beneath the soil largely intact.

Because the enclosure is only legible as a cropmark, there is little to see on the ground in the conventional sense. The best conditions for cropmarks to appear are during dry summers, when water stress in the soil accentuates the differential growth above buried features, which is presumably why the June 2018 imagery captured it so clearly. For anyone curious enough to look, pulling up the relevant coordinates on Google Earth or Apple Maps will show the ring more clearly than any site visit is likely to. The land at Knockbrack is ordinary agricultural ground, and the enclosure sits within it quietly, waiting for someone with the right tools or the right dry summer to notice it again.