Stand in the flat pasture there, surrounded by gently rolling countryside, and nothing will betray what lies beneath the grass. The site is entirely invisible at ground level, which places it in a particular category of archaeological place: known to exist, but experienced only as an absence.

What revealed it was an aerial photograph, reference GSIAP R 191/2, which captured the outline of a circular enclosure from above. Circular enclosures of this kind are often referred to locally as forts, a broad term that in the Irish context usually indicates a ringfort, the most common monument type in the Irish landscape. Ringforts were typically enclosed farmsteads of the early medieval period, their circular banks and ditches defining a domestic space rather than a military one, despite the name. At Knockanacartan, local tradition had preserved the memory of a fort on the spot even as the physical traces disappeared, and the aerial photograph confirmed that memory had a basis in fact. The crop or soil marks visible from the air suggest that the enclosure's outline survives as a buried feature, its circular form pressed into the ground well below the surface of the modern field.