An aerial photograph taken that summer captured something invisible to anyone walking the tillage field below: a series of cropmarks betraying the outline of an enclosure, its surrounding ditch, and, faintly, what may be a souterrain buried within.

Cropmarks form when buried features affect the growth of crops above them; a filled-in ditch retains more moisture and produces lusher, darker growth, while a buried wall does the opposite. The photograph from July 1999 shows a rectilinear enclosure defined by a fosse, essentially a defensive or boundary ditch, with a notable indentation along its western side. Extending outward from the enclosure are two further linear fosses consistent with an early field system, suggesting this was once an organised agricultural or settlement landscape. Most intriguingly, a dark green cropmark within the south-western sector of the enclosure points to an internal structure, tentatively identified as a souterrain. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlement in Ireland, used variously for storage, refuge, or ventilation. Whether the Deerpark example is genuinely subterranean remains unconfirmed; the identification rests entirely on that aerial image and has not, as far as the record indicates, been verified by excavation.

There is something quietly strange about a site whose existence is known only through a photograph taken on a specific date, from a specific altitude, in the right conditions of crop growth and summer light. The field at Deerpark gives nothing away on the surface. The enclosure, its field system, and the possible souterrain within remain beneath the soil, legible only in that brief annual window when the crops above speak for what lies below.