The ruins on a low rise north-east of Kill Abbey Road in south County Dublin survive to gable height, and the double bellcote still crowns the western end, but the walls themselves tell a more complicated story: a pre-Norman single-cell building, its side walls projecting slightly beyond the gable faces to form antae, a distinctively Irish early medieval feature, onto which a chancel and round chancel arch were later grafted, the join still visible because the chancel walls simply do not bond into the original masonry.

The site at Clonkeen, as it was originally known, is attributed to St Fintan, with a founding tradition reaching back to the 6th century. By the time of a regal visitation in 1615, both the church and its counterpart at Dalkey had their rectories linked to Christ Church in Dublin, with one Owen Ellis serving as curate of both; the nave walls were reported in repair, but the chancels were already in ruins. When the antiquarian W.F. Wakeman visited in 1896 and recorded his observations for the Journal of the Royal Society of Antiquaries of Ireland, he noted that the eastern window of the chancel was characteristic of twelfth or, at the latest, thirteenth-century work, suggesting the nave itself was considerably older still. The whole structure is built of coursed granite, the blocks tending to be larger in the later medieval addition, and somewhere in the fabric a fragment of a possible cross-slab has been reused as a corner-stone at the south-west angle of the church.

The church sits within a roughly rectangular graveyard enclosed by a post-1700 stone wall. The wider complex includes a holy well, a bullaun stone (a large stone with a carved hollow depression, associated with early Christian and pre-Christian ritual use), two grave slabs, a stone font, and the base of a stone cross. Two crosses that once stood along the former laneway into the graveyard have been removed and are now held by the Office of Public Works in Trim, County Meath. Visitors who look closely at the west gable will find the reconstructed lintelled doorway, and along the south wall a later round-arched entrance inserted when the original entrance style had fallen out of fashion; Wakeman noted that the lower portion of the original doorway was likely buried beneath accumulated graveyard soil even in his day, so the ground level around the walls is worth bearing in mind as you walk the site.