There is nothing to see at Prusselstown, and that is precisely the point. On a gently sloping pasture field facing south-west in County Kildare, the ground gives no hint that anything lies beneath it. No earthwork, no mound, no depression. The site exists, for practical purposes, only as a ghost in a photograph taken from the air in 1967.

That photograph, taken as part of the Cambridge University Collection of Aerial Photography, revealed something the grass had long since swallowed: the cropmark of a fosse, a defensive ditch, tracing a roughly circular area of approximately 40 metres in diameter. Cropmarks appear when buried features affect how crops or grass grow above them, with ditches often producing lusher, darker growth due to retained moisture, making the invisible briefly legible from altitude. The shape and dimensions are consistent with a rath, the type of enclosed circular farmstead built throughout early medieval Ireland, typically surrounded by one or more earthen banks and ditches. If that interpretation is correct, the bank and any internal structures have been completely levelled, leaving only the cut of the original fosse detectable beneath the surface. The same aerial photograph also picked up what may be an associated field system to the south-east of the enclosure, and a possible rectangular enclosure in the adjacent field to the south-west, suggesting that whatever activity took place here was not confined to a single structure but extended across the surrounding landscape.