The only way it announces itself is from the air, where a difference in crop growth betrays a buried boundary beneath the soil, a phenomenon known as a cropmark. Where subsurface stonework or ditches affect moisture and nutrients in the ground, the plants above grow at slightly different rates, and from altitude the pattern becomes legible. In this case, what emerges is the arc of what may once have been an oval enclosure, orientated east to north, measuring roughly 39 metres north to south and 32 metres east to west.

The enclosure is classed as possibly univallate, meaning it would have had a single surrounding bank or ditch rather than multiple concentric rings. Enclosures of this kind are often associated with early medieval settlement in Ireland, though without excavation the date and function of this particular example remain uncertain. What makes the Gortnacrusha site additionally interesting is its relationship to a neighbouring feature: immediately to its north-east lies another possible rath, the term used for a circular earthen enclosure that typically served as a farmstead in the early medieval period. Whether the two features were contemporary, or belong to different phases of activity in the landscape, is an open question. The cropmark image comes from the Cambridge University Collection of Aerial Photography, and represents one of the quieter ways in which Irish archaeology has been mapped, not through excavation or fieldwork, but through a pilot flying over farmland and noticing that the grain is telling a story.