This is the ghost of an early ecclesiastical enclosure, the kind of broadly circular boundary, defined by a fosse (a ditch), that early Irish monasteries and church settlements typically used to demarcate sacred ground from the secular world beyond. No earthwork survives above the surface. The only reason anyone knows it is there at all is an aerial photograph taken in 1968, in which a dry summer revealed the outline as a cropmark, the differential growth of grass over a buried ditch tracing the arc in muted tones from above.

The enclosure wraps around the parish church of Kilmore, a building considered to be probably of early origin, now set within a large rectangular graveyard bounded by masonry walls. The aerial photograph shows the circular feature running from the southeast to the southwest of the church, continuing into the field to the east of the graveyard, and it appears that the original enclosure predates, and does not align with, the later rectangular graveyard boundary. Archaeological testing carried out in 2011 in the field immediately east of the graveyard confirmed the fosse was real, not a trick of the light. Excavators found it running north to south, three metres wide, extending at least twenty-three metres from the graveyard wall. That same investigation turned up considerably more besides: pits, a largely ploughed-out burnt mound, and what appear to be drains from an old field system. Prehistoric and medieval pottery was recovered alongside struck flints, suggesting the landscape around Kilmore had seen human activity across a very long span of time, long before any church was built within this enclosure.