In a field in Fanaghs, County Kildare, there is no visible mound, no standing stone, no earthwork that catches the eye at ground level. What exists instead is a ghost, approximately 28 metres across, legible only from the air: a circular cropmark that betrays the presence of something buried beneath the soil.

Cropmarks form when buried features, whether ditches, walls, or pits, affect the growth of whatever is planted above them. Soil that has been disturbed or that retains more moisture tends to produce taller, greener crops; compacted or stony ground beneath the surface produces shorter, paler ones. From above, particularly during dry summers when these differences are exaggerated, the outlines of long-vanished enclosures can emerge with surprising clarity. The Fanaghs example, a near-perfect circle of this kind, was identified in aerial imagery captured on 28 June 2018 and brought to wider attention through the work of Edward O'Riordan, with the record compiled by Caimin O'Brien. Circular enclosures of broadly this scale are commonly associated with the early medieval period in Ireland, when ringforts served as enclosed farmsteads, though without excavation the date and precise function of any individual example cannot be confirmed. The mark at Fanaghs, roughly 28 metres in diameter, sits at the smaller end of that general range.

The site is, by its nature, one for the imagination rather than the visit. There is nothing to see at ground level, and the shape reveals itself only when viewed from altitude, as in the Google Earth imagery through which it was first noticed.