Cropmarks form when buried features, walls, ditches, or filled pits, affect the growth of crops above them, causing subtle variations in colour and height that become legible in aerial photographs, especially during dry summers when the soil is stressed. The enclosure at Grangefertagh was captured in precisely these conditions in August 1996, emerging briefly into the photographic record before fading again into the ordinary field.

What the aerial photographs also revealed is that this enclosure does not stand alone. A second enclosure adjoins it immediately to the north-east, the two forming a conjoined pair, their boundaries touching or overlapping. Conjoined enclosures of this kind are known elsewhere in the Irish landscape and may represent successive phases of activity on the same site, or related but distinct uses of adjacent spaces. Whether these are the traces of early medieval farmsteads, ritual enclosures, or something else entirely, the photographs alone cannot say. The name Grangefertagh has its own quiet interest: "grange" typically points to monastic agricultural land, suggesting that this part of Kilkenny was once managed by a religious house, which adds a possible layer of context to whatever once stood within these circular boundaries.