Its existence is suggested not by stone, earthwork, or any surface feature, but by a cropmark captured in an aerial photograph taken in 1997 by Dr DDC Pochin Mould. Cropmarks appear when buried structures affect the growth of vegetation above them, typically causing crops or grass to ripen at different rates, leaving faint geometric shadows that are only legible from the air. What the photograph appears to show is a roughly three-sided shape, with two straight sides running to the west and north, joined by a curving third side, underlying or immediately to the north of the early ecclesiastical enclosure that already surrounds the graveyard.

That ecclesiastical enclosure is itself of considerable age, the kind of roughly circular boundary that in Ireland typically marks the perimeter of an early Christian monastic or church site. The possibility that an even earlier enclosure lies beneath it, predating or perhaps informing the layout of the later religious site, is the quietly interesting part of this story. Whether it represents a prehistoric settlement, a ritual boundary, or something else entirely remains unknown. There are no visible remains at ground level, and no excavation appears to have been carried out to confirm what the cropmark suggests. For now, the enclosure at Cloghmacsimon exists as a shape in a single photograph, a geometry pressed into the earth and visible only when the conditions of light, season, and altitude align just right.