On the south-eastern margins of the Curragh, a broad expanse of open grassland in County Kildare long associated with military training and horse racing, something faint and circular interrupts the turf. It is not visible to a casual walker and was not recorded on the ground at all; it emerged only when aerial photography carried out by the Department of Defence in 1999 revealed a pattern that the grass itself had quietly preserved.

What the aerial image showed was a ring-ditch, a roughly circular feature most commonly associated with prehistoric burial or ritual activity. Ring-ditches are the ploughed-out or otherwise reduced remains of barrows, earthen mounds raised over burials, and they survive in the landscape primarily as crop marks or, as here, as differences in vegetation growth where the soil retains more moisture along the line of an ancient ditch. In this case, a band of noticeably lusher grass, some 2.3 metres wide, traces an almost perfect circle measuring approximately 3.8 metres east to west and 3.6 metres north to south. That circle sits on top of a low, subcircular mound, which is itself modest but measurable, somewhere between 0.6 and 1.5 metres in height, and extending roughly 17.5 metres north to south and 15.4 metres east to west. The mound may be natural in origin, though the presence of the ring-ditch above it suggests it was at some point considered a meaningful or appropriate place to mark.