What betrays it is not stonework or earthwork but a cropmark, the faint differential in how crops grow over buried ground, revealing the outline of a fosse, a defensive or boundary ditch, that once defined a small circular enclosure. The feature was captured in an aerial photograph taken in July 1989, one of those moments when the right angle of light and the right stage of the growing season conspire to make the invisible legible.

Ring-ditches of this kind are generally understood as the buried remains of prehistoric funerary or ceremonial monuments, sometimes the eroded remnants of a round barrow where the central mound has long since been ploughed away, leaving only the encircling ditch as a ghost beneath the soil. The enclosure at Poulnareagha is modest in scale, with a diameter of around ten metres, placing it at the smaller end of such features. What gives the site an additional layer of interest is the presence of a possible second circular enclosure approximately 170 metres to the northwest, raising the question of whether these two features were related in function or simply neighbours across the centuries, each accumulating its own quiet history before both disappeared beneath the fields.