Nothing breaks the surface of this enclosure in the townland of Ardoyne; no earthwork, no visible bank, no trace of any entrance. It exists, for the moment, almost entirely as a cropmark, the kind of ghostly outline that only becomes legible when viewed from above, when differential moisture retention or crop growth betrays the line of a ditch that has been filled in for centuries.

Cropmarks form when buried features such as ditches or pits retain moisture differently from the surrounding undisturbed soil, causing the crops above them to grow at slightly different rates. In dry summers particularly, the contrast becomes sharp enough to photograph from the air or from satellite. The Ardoyne enclosure is one of several such features visible in the same large field, alongside a ring-ditch located roughly 100 metres to the west-northwest. A ring-ditch is typically the ploughed-down or silted remnant of a prehistoric burial mound or a circular earthwork. The enclosure itself is subcircular to oval in plan, measuring approximately 12.5 metres east-west by 14.8 metres north-south, with a continuous ditch around 1.5 metres wide that can be traced along its entire circuit. Unusually, there is no evidence of an entrance gap anywhere in that circuit, which sets it apart from the typical form of an Irish ringfort or rath, where a clear break in the ditch marks the way in. What that absence signifies, whether an unusual construction method, a ritual enclosure, or simply a gap that has since silted beyond recognition, is not yet established. The site sits at around 91 metres above sea level on relatively flat ground, roughly 400 metres from a second enclosure to the north-northwest, and about 500 metres from a ruinous church and associated graveyard near the Carlow border, all within the same townland.