Yet St. Finian's, in the townland of Glebe, manages both. The west gable still stands to roughly seven metres, its two tall buttresses curving together to form a projecting arch over a narrow slit window, an arrangement that may once have supported a bellcote. The east end of the building has been reduced to tidy flat-topped foundations by county council conservation work, which also left the mortar joints conspicuously repointed in a ribbon style that a 1978 survey noted with some concern. The overall effect is of a long, roofless shell, nearly thirty metres end to end, occupying the western corner of a rectangular graveyard a hundred metres or so from King John's Bridge over the Griffeen River.

The church takes its name from the esker, a ridge of glacial gravel that once marked the boundary between Leath Conn and Leath Mogha, the ancient northern and southern divisions of Ireland. That geographical significance translated into political weight: Prince John reserved Esker as one of four royal manors of Dublin, alongside Newcastle Lyons, Saggard, and Crumlin, all of them administered for the Crown by officials called Seneschals whose office survived well into the nineteenth century. The church and the parish of Esker were granted to St. Patrick's Cathedral, and by 1615 the Royal Visitation of the Diocese of Dublin was recording a curate named Richardus Wiborow and noting that the vicar had been deprived of his position for non-residence. By 1630, Archbishop Bulkeley's visitation found things considerably worse: the church was described as altogether ruinous, nothing standing but the walls. That same visitation noted that a local man, Mr. Lamoruke Nottingham of Ballyowen, was being identified as a maintainer of priests and friars in the parish. The 1654 to 1656 Civil Survey recorded that the Vicars Choral of St. Patrick's Cathedral held fifteen acres of glebe land here.

The most rewarding thing to seek out inside the shell is the two-light window in the south wall, which Henry A. Wheeler dated to around 1400. Each light has a cusped trefoil head set under a slightly ogee arch, with concave spandrels at the corners; the whole window is splayed inward and sits in a round-headed embrasure. It is the kind of careful stonework that feels out of place in what the documents already called a ruin by the seventeenth century. Directly above it, placed upside down during conservation, is a spandrel fragment from a second window of similar character, its original position unknown. Two putlog holes near the west end of the north wall, square openings of around twenty centimetres, suggest there was once a timber floor or stair at that end. The graveyard remains in use, so the site is generally accessible, and Rocque's 1760 map of County Dublin records the church ruins already in much the state you see now.