In a field in County Kildare, the ground holds a secret that only reveals itself from the air. Where a rath once stood, its earthworks long since levelled by centuries of agriculture, a curvilinear cropmark appeared in a 1989 aerial photograph, hinting at something buried beneath the surface. The feature is thought to be a souterrain, an underground stone-lined passage or chamber typically associated with early medieval ringforts, used variously for storage, refuge, or concealment.

The rath itself, a circular earthen enclosure of the kind built across Ireland during the early medieval period, has been almost entirely erased from the landscape. What the aerial photograph captured was not the structure directly, but the faint signature it leaves on growing crops, where buried stonework or disturbed soil causes vegetation above to behave differently, producing a pattern visible only at altitude and in the right season. The souterrain, if that is indeed what lies below the southern sector of the former enclosure, would have been an integral part of the original settlement, entered from within the rath's interior and descending into the earth.