At Rathkennan in County Tipperary, a roughly circular form approximately thirty metres across emerges only when viewed from the air, disclosed not by any upstanding stonework or earthwork but by the differential growth of crops above buried features, a phenomenon known as a cropmark. The northern quadrant does not even appear in the aerial image, leaving the full shape a matter of inference rather than certainty.

The site was identified from an aerial photograph taken in July 2005, on a gradual north-west-facing slope in gently rolling, hilly terrain that is under tillage. Cropmarks of this kind form when buried ditches or walls affect the moisture and nutrients available to plants growing above them, causing subtle but visible variations in colour and height at certain times of the growing season. The circular form at Rathkennan is consistent with the enclosures, typically defined by a bank and external ditch, that are found widely across the Irish landscape and that served a variety of purposes over several millennia, from settlement to ritual use. Whether this particular feature belongs to the prehistoric period or a later era cannot be determined from the cropmark alone, and without ground investigation it remains a possibility rather than a confirmed site.