That is, in a sense, exactly what makes it worth knowing about. Somewhere in a cultivated field in the Knockgraffon area of County Tipperary, the outline of a circular enclosure lies buried beneath the soil, invisible to anyone standing in the field and entirely unreadable from the ground. Its existence is known only because of what appeared briefly in an aerial photograph taken in 1974.

The enclosure was identified as a cropmark on a Geological Survey of Ireland aerial photograph from April of that year. Cropmarks form when buried features, walls, ditches, or filled-in pits, affect the moisture and nutrient content of the soil above them, causing the crops growing overhead to ripen or wither at slightly different rates. From the air, under the right conditions, these differences trace the outlines of structures that have otherwise vanished entirely. The circular shape that emerged in the 1974 photograph is consistent with the kind of early enclosure, typically a ringfort or enclosed farmstead, that occurs widely across the Irish landscape. The site sits on flat ground in a small river valley, with a channelised stream running immediately to the east. A second enclosure of the same type may have existed around 200 metres to the west, suggesting this was once a settled, perhaps reasonably active, stretch of valley floor.