What exists at Oldgrange in County Kilkenny is a roughly rectangular enclosure measuring approximately 50 metres along its northwest to southeast axis and around 37 metres across, but it survives not as an upstanding earthwork or visible ruin, rather as a cropmark, a ghostly outline that appears only in satellite imagery taken at the right moment in the agricultural year. The enclosure lies in tilled land, and it was the differential growth of crops over buried features, drawing moisture unevenly from the soil, that betrayed the presence of two concentric ditches, or fosses, lying roughly 7 metres apart, beneath the surface. Cropmarks of this kind are one of the more quietly remarkable tools in the archaeologist's repertoire, allowing buried landscapes to be read from above without a single trowel being lifted.

The site came to light in July 2018, when Jean-Charles Caillère and Simon Dowling identified the enclosure while examining Google Earth Pro imagery captured on 14 July of that year. The double-fosse plan, with an inner and outer ditch enclosing the rectangular space, suggests a monument of some consequence, though its date and precise function remain undetermined. A cropmark of a field boundary running approximately 110 metres southeast from the monument's southeastern angle may be contemporary with the enclosure itself, hinting at an organised landscape once surrounding it. A further cropmark of a boundary running roughly 70 metres to the west-southwest is likely later, and intriguingly it appears to cut between the two fosses in the southwestern quadrant, suggesting that by the time that boundary was laid down, memory of the enclosure's layout had been lost. The northeastern edge of the outer enclosure has been slightly clipped by a modern field boundary, though the monument is otherwise largely intact beneath the ploughsoil.