No stone, no mound, no visible feature of any kind. What gives it away is a dry summer and a low-flying aircraft. In July 1989, an aerial photograph of fields near Donaghmore in Co. Kilkenny captured a cropmark, the faint but readable trace of a ring-ditch buried beneath the soil. A ring-ditch is typically the surviving remnant of a ploughed-out burial mound or round barrow; the circular ditch that once surrounded the monument has long since been filled in, but the disturbed earth holds moisture differently from the undisturbed ground around it, causing the crops above to grow at a slightly different rate. From the air, that difference resolves into a ghostly circle pressed into the grain.

What makes the Donaghmore example particularly interesting is the company it keeps. Within a radius of roughly 200 metres, the same method of aerial reconnaissance has revealed at least three other buried features: a second ring-ditch approximately 150 metres to the north-west, a smaller enclosure around 40 metres to the south, and a larger enclosure roughly 190 metres to the east-north-east. Enclosures of this kind could represent anything from early settlement sites to field boundaries or ceremonial spaces, and their proximity to the ring-ditches suggests this corner of Kilkenny was, at some point in prehistory or the early medieval period, a place of considerable activity. None of these features were known from ground-level survey; all were identified solely from cropmark evidence captured in aerial photographs.