It measures roughly 90 metres across, making it considerably bigger than a typical Irish ringfort, and it has never been excavated. Nobody is entirely certain what it is. The only way it has ever been seen clearly is from the air, where it shows up as a cropmark, the faint but readable trace left when buried features affect the growth of vegetation above them. Aerial photography has long been one of archaeology's more quietly effective tools in Ireland, revealing boundaries, ditches, and enclosures that are completely invisible at ground level.

The feature sits within what was the post-1700 deerpark associated with Killua Castle, a large Anglo-Irish estate roughly 550 metres to the east. A ringfort, the type of enclosed circular settlement that was widespread in early medieval Ireland, lies only 90 metres to the north, and two further landscape features have been identified approximately 160 metres to the north-north-east. The clustering of such traces in a single area is not unusual on Irish demesne lands, where the deliberate management of parkland sometimes had the unintended effect of preserving earlier features beneath the surface. What complicates matters here is the sheer scale of the circle. At 90 metres in diameter it exceeds what would normally be expected for a ringfort or similar enclosure, which has prompted the possibility that it may not be archaeological at all. Some circular cropmarks of this size turn out to reflect geological processes, the legacy of how glacial or other natural forces shaped the underlying ground rather than any human activity.