In a level Kildare pasture, the ground holds a secret that is only legible from the air. What looks like ordinary farmland at Clonagh conceals the ghost of a large circular enclosure, roughly 130 metres in diameter, betrayed at the surface only by a curving line of overgrown earthen field boundary. The rest of it has all but vanished into the soil.

Aerial photography changed what we know about this site. On GSI photographs N469 and N470, a cropmark appears: a faint arc tracing the probable line of a fosse, which is a defensive or boundary ditch, along the western sweep of the enclosure, running from the south-southwest around to the north-northwest. Cropmarks form when buried features such as ditches or walls affect how vegetation grows above them, making the underlying archaeology visible only in certain light or during dry spells when crops stress differently over disturbed ground. The combination of that cropmark and the surviving earthen boundary suggests a circular enclosure of considerable size, though its date and precise function remain unconfirmed. Large circular enclosures of this kind in Ireland are often associated with early medieval settlement or ritual use, though without excavation it is difficult to say more with confidence about this particular example.