What we know of it comes from a single aerial photograph taken between 1973 and 1977, which revealed a large rectangular cropmark, one of those ghostly outlines that appear in parched grass or ripening grain when buried walls or ditches affect how plants grow above them. Two parallel lines extend from one side at right-angles, suggesting an entrance feature or an attached structure of some kind. On the ground, there is nothing to see at all.

When an inspector visited the site in 1983, the archaeology yielded no new physical evidence, but the conversation around it proved interesting in its own way. Local tradition held that Belderg itself, the townland's name, preserves the memory of a battle fought there long ago, and that the victims of that battle were buried in a triangular field at the northern tip of the neighbouring townland of Skinnagin. It is the kind of oral memory that persists in Irish placenames with remarkable tenacity, connecting landscape and event across generations without a single written source. The cropmark was formally recorded as a potential site on that basis, appearing first in the non-statutory Sites and Monuments Record issued in 1985 and then in the statutory Record of Monuments and Places issued in 1996. Archaeologists have been careful, however, not to classify it as a confirmed battlefield. Local tradition is suggestive, not conclusive, and the rectangular enclosure visible from the air could have any number of explanations.