A low, unremarkable rise in a Kildare pasture conceals something that only became visible from the air, and even then only briefly, under the right conditions. In 1973, an aerial photograph taken as part of the Cambridge University Collection of Aerial Photography captured a pair of cropmarks at Russellstown: a circular enclosure overlain and apparently enclosed within a larger rectangular one, measuring roughly 70 metres on its northeast-to-southwest axis and around 60 metres northwest-to-southeast. Cropmarks form when buried features, walls, ditches, or filled pits, affect the growth of surface vegetation above them, producing faint but legible outlines that become readable from altitude. Walk the field today and there is nothing to see; no earthworks, no raised banks, no visible trace of either shape.

The circular enclosure is the older and more intriguing of the two forms. Circular enclosures in the Irish landscape are typically associated with early medieval settlement, the ringfort tradition that once produced thousands of such sites across the country. Here, though, the circular feature appears to have been absorbed into, or overlain by, a rectilinear boundary of considerably larger extent, possibly a later field system. What makes the relationship between the two especially curious is that neither feature appears on the first edition six-inch Ordnance Survey map of 1839, which is generally reliable for earthworks and banks that were still legible in the nineteenth century. Their absence from that map suggests that whatever physical presence they once had was already gone well before the surveyors passed through, leaving the 1973 photograph as the sole record of their existence.