Walk the field and you would notice nothing unusual, no earthwork, no dip in the soil, no gathering of stones. The site exists, as far as the casual observer is concerned, only in the sky.

In 1971, an aerial photograph catalogued as FSI 3.698/9 captured what ground-level inspection had apparently never revealed: the partial outline of a circular enclosure roughly 23 metres in diameter. Aerial photography of this kind works by detecting crop marks or soil marks, subtle variations in vegetation colour or growth rate that betray buried features beneath the surface. Faster-growing or differently coloured crops over a filled ditch, for instance, can trace an entire enclosure from altitude that leaves no impression whatsoever underfoot. Circular enclosures of this general type are associated across Ireland with a wide range of periods and functions, from early medieval farmsteads to prehistoric ritual sites, and without excavation it is not possible to say what this particular one represents. The record was compiled by Geraldine Stout and Padraig Clancy, researchers whose work has documented many such fugitive sites across the Irish landscape.

For anyone curious enough to seek it out, the location is a field of pasture on elevated ground to the west of Brides Glen, in an area that has seen considerable suburban development around Cherrywood in recent decades. The surrounding landscape has changed substantially since that 1971 photograph was taken, and access to private farmland would require the landowner's permission. The site itself offers nothing visible at ground level, which is, in its own way, the point. What makes it worth knowing about is precisely that absence, the reminder that the Irish landscape holds any number of features that only reveal themselves under particular conditions of light, season, and altitude, and that the absence of visible remains does not mean the absence of history.