The letters read DOM, interpreted by scholars as an abbreviation for Domini, Domino, or possibly Deo Optimo Maximo. This is the bullaun stone of Kill of the Grange, a bullaun being a type of ancient stone with deliberately carved basin-like depressions whose precise function, whether ritual, practical, or both, remains genuinely unresolved. The stone sits approximately ten metres west of the graveyard wall, just outside the boundary, and in 1896 a contemporary observer called it perhaps the most curious remain of its class in Ireland.

The site grew from the early Christian monastery of Clonkeen, meaning pleasant meadow or pasture in Irish, founded by St Fintan in the sixth century on a low rise in what is now the barony of Rathdown. By 1178 or 1179, a charter associated with St Laurence listed it among the possessions of Christ Church Cathedral in Dublin, and around 1200 the Archbishop of Dublin confirmed grants to the church made by William Marshal, Earl of Pembroke, along with Isabella his wife and Raymond le Gros. King John further confirmed those holdings, noting that Clonkeen had originally been a donation of Ruad, son of Donal, King of Leinster. The pre-Norman single-cell church, a National Monument, was later extended eastward by a late medieval chancel, and Peter Harbison's 1970 description noted the small church's antae, which are projecting side walls characteristic of early Irish stone churches, as well as a partly reconstructed flat-headed doorway. A holy well lying 37 metres to the northwest of the church was, according to an 1896 account, known locally as the British Well, a name no one could quite explain, though local placename memory suggested a connection to St Mogue, the sixth and seventh-century saint who died at Ferns in 624 and who may have sojourned here with British ecclesiastics on one of his journeys from Wales.

The ruins and graveyard are now surrounded by St Fintan's Park housing estate, which gives the site an unexpectedly quiet, residential feel. The enclosing graveyard wall dates from after 1700, and within the graveyard are the bases of two early medieval crosses, though two further crosses removed from the former laneway into the graveyard are now held at the OPW depot in Trim, County Meath. The holy well was filled in during the mid-1980s and leaves no visible trace today. A structure known locally as Kill Abbey, a medieval house, stands about 50 metres west of the graveyard wall. The monastic enclosure itself was only identified in 2018, when archaeologist Paul Duffy uncovered its outline during excavations prompted by drainage works for a nearby residential development, a reminder that the ground here still holds more than is visible on the surface.