The site at Killamurren takes its name from the Irish Cill Atha Muirín, meaning the Church of Muirín's Ford, and the enclosure that once defined it was substantial: roughly seventy metres north to south and sixty metres east to west, a sub-circular boundary of the kind that typically marks an early medieval ecclesiastical settlement in Ireland. That shape, a broad rounded enclosure rather than a rectangular field boundary, is a characteristic signature of early Christian monastic or church sites, where the circular form carried both practical and symbolic weight. By the time the Ordnance Survey recorded it on the six-inch map of 1935, the enclosure was still legible in the landscape. It is largely gone now, displaced by farm buildings.

When Patrick Power recorded the site in 1923, there was considerably more to see. He described a circular enclosure of roughly half an acre containing the traceable foundations of a small church, measuring twenty-seven feet by fifteen feet, which falls within the range typical of simple early medieval Irish oratories. To the south of those foundations, he noted a bullán stone and traces of other structures. A bullán is a large stone, often a boulder, with one or more artificial cup-shaped hollows ground into its surface; such stones are frequently associated with early ecclesiastical sites in Ireland and may have served liturgical, medicinal, or grinding purposes, though their precise function is still debated. None of these features, neither the church foundations, the bullán, nor the ancillary traces, remain visible today.