Heavily overgrown and visible only from the air, it had the silhouette of antiquity without any of the substance.

The site first appeared as a "Potential Site Aerial Photo" in the Sites and Monuments Record in 1992, and was carried forward into the Record of Monuments and Places in 1996. Both designations were based on aerial photography alone, the kind of oblique or vertical imagery that can make a modern field boundary look convincingly like a prehistoric enclosure, particularly when vegetation has been left to run wild. When a ground inspection was finally carried out in 1999, the structure turned out to be a small circular enclosure defined by a drystone wall of modern construction. Drystone walling, built without mortar by stacking and wedging stones together, is a technique used across Ireland for centuries, but the wall here offered none of the diagnostic features that would suggest early medieval or prehistoric origin. The circle of suspicion closed, and the site was quietly reclassified.

What makes Rannagh worth a moment's attention is less the enclosure itself than what the episode illustrates about the limits of remote survey. Aerial photography has been one of the most productive tools in Irish landscape archaeology, capable of revealing crop marks, soil discolouration, and earthwork shadows invisible at ground level. But the method is not infallible, and the gap between the 1992 listing and the 1999 inspection meant that for several years this unremarkable modern wall carried the provisional status of an ancient monument. The overgrowth that helped generate the confusion is still there.