There is nothing to see at Boley Little. That is precisely what makes it interesting. Somewhere beneath a worked tillage field on a gentle south-facing slope in County Kildare, the buried outline of a circular enclosure sits invisible to anyone walking across it, its existence known only because a camera mounted in an aircraft happened to pass overhead in 1968 and caught the ground telling the truth.

The photograph in question, taken as part of the Cambridge University Collection of Aerial Photography and catalogued as CUCAP AVM 22, captured what is known as a cropmark. This is a phenomenon in which buried features, such as ditches or walls, affect the growth of crops above them: a filled-in fosse, a ditch that once ringed a settlement or farmstead, retains more moisture than the surrounding soil, and the plants rooted above it grow fractionally taller or greener, tracing the old boundary in the harvest. At Boley Little, the cropmark revealed a fosse, the term for a defensive or boundary ditch, enclosing a roughly circular area of approximately forty metres in diameter, with what appears to be a smaller rectangular field attached to its southern side. No trace of this structure survives above ground today. A second levelled enclosure of similar character lies around twenty metres to the north, suggesting this corner of Kildare was once a more organised and inhabited landscape than the open farmland now suggests.