The field at Rathbeagh in County Kilkenny looks like ordinary tillage land, worked and reworked across the seasons. But from the air, a different geometry emerges: cropmarks, the faint differential colouring that ripening grain produces over buried ditches and earthworks, reveal an elaborate circular enclosure roughly forty metres across, defined by a fosse, which is an excavated ditch typically used to demarcate or defend a settlement, with what appears to be an entrance opening in the south-eastern quadrant. The cropmark pattern is complex enough that a single visit, even at the right time of year when crops make buried features most legible, would give little away to a person standing at the field's edge.

What the aerial photographs capture is not one monument but probably two, folded together over time. Inside the larger enclosure, a curving internal fosse arcs from the north-east around through the east and south to the south-west, before running back out to meet the outer ditch. The most plausible reading of this arrangement is that an earlier, smaller enclosure once occupied the site, and that when the larger enclosure was built, it incorporated part of the older ditch, specifically the north-western stretch, rather than simply replacing it. Extending further still, a large conjoined curvilinear enclosure pushes westwards from the south-western quadrant, curving around until it meets a linear field boundary running roughly north-east to south-west. Around all of this lies the ghost of an extensive rectilinear field system, now ploughed flat, but still visible on the first edition six-inch Ordnance Survey map published in 1839 and on the revised edition of 1900, suggesting the surrounding landscape retained some upstanding structure well into the nineteenth century before agricultural improvement finally levelled it.