At Griffinrath in County Kildare, something buried beneath a farmer's field gives itself away only from above. A roughly circular enclosure, around 48 metres in diameter, shows up as a cropmark on aerial photography, its outline traced not by stone or earthwork but by the differential growth of crops over whatever lies beneath the soil. A possible entrance gap at the south-south-east and what appears to be an annexe to the north-west add further definition to the shape, suggesting a site with some complexity, even if its date and function remain unconfirmed.

Cropmarks form when buried features, such as ditches, pits, or walls, affect how plants grow above them. Ditches retain moisture, producing lusher, taller crops; compacted surfaces or stone foundations do the opposite. Seen from the air in dry summer conditions, these variations in growth can reveal the outlines of enclosures, field systems, or settlements that are otherwise invisible at ground level. The Griffinrath enclosure came to light through a Google Earth photograph taken on 28 June 2018, with the detail supplied by Colin Flynn. Circular enclosures of this kind are commonly associated with early medieval ringforts in Ireland, though without excavation it is impossible to say whether this example is a ringfort, a prehistoric enclosure, or something else entirely. The annexe to the north-west is a particularly notable feature; annexes sometimes served as stock enclosures or as secondary activity areas attached to a main settlement.