A series of aerial photographs taken in 2004 revealed a cropmark tracing the outline of a circular enclosure roughly twenty metres in diameter, its presence betrayed only by the way crops grow slightly differently above a buried ditch. That ditch, or fosse, once defined the boundary of whatever lay within.

Cropmarks appear when buried features affect the moisture content of the soil above them. A filled-in fosse retains more water than the surrounding ground, so crops rooted over it tend to grow taller and greener, outlining the vanished structure in living geometry. The enclosure at Toberbeg sits on a slight north-south ridge, a detail that may be significant: elevated ground was frequently chosen for enclosed settlements, ritual sites, or places of local authority during the early medieval period in Ireland. Circular enclosures of this general scale are often associated with ringforts, the most common archaeological monument type in the Irish landscape, though without excavation it is impossible to say with certainty what this particular site was used for or when it was built.