A cropmark, roughly eighty metres in diameter, traces the outline of an ancient enclosure, its shape preserved not in stone or earthwork but in the differential growth of crops above whatever ditches or banks were dug here long ago. Cropmarks form when buried features affect how plants grow overhead, with lusher or poorer growth betraying the presence of filled-in ditches or compacted walls, and from altitude the pattern becomes a kind of negative photograph of a vanished structure.

The enclosure at Balreagh was identified from Google Earth aerial imagery, with a photograph taken on 18 April 2014 capturing the mark clearly enough to be recorded. At eighty metres across, this is a substantial site. Ringforts, the most common enclosed settlements in early medieval Ireland, tend to run between twenty and fifty metres in diameter, so an enclosure of this scale sits outside the typical range and raises questions about its original function, whether as a large ceremonial or political site, an ecclesiastical enclosure, or something else entirely. Without excavation, the date and purpose remain open. The record was compiled by Caimin O'Brien, working from details provided by Jean-Charles Caillère, and the site entered the record in September 2019.