That small cartographic error, corrected between the first and third editions of the six-inch map, points to something genuinely complicated about these ruins in Ballynakill: a building that has been medieval parish church, Burke family chapel, and eighteenth-century Catholic place of worship in turn, each phase leaving its mark on the fabric, and none of them quite erasing the one before.

The main structure is a rectangular building, roughly 22 metres long and 7.6 metres wide, oriented east to west in the usual manner for a Christian church. Much of it has collapsed or eroded to low courses, but the east gable still stands, along with sections of the south wall. Two window openings in the east gable and traces of a centrally placed doorway in the west gable likely date from an eighteenth-century refurbishment, when the first edition of the Ordnance Survey map records it as an "R.C. Chapel (in Ruins)", implying it had already fallen out of regular use by then. A blocked opening above one of the south wall windows hints at a former loft at the west end, a feature sometimes added when congregations grew or when a building was adapted for new uses. Adjoining the east end of the south wall is a side-chapel in considerably better condition, measuring around 9.5 by 6.2 metres. It is entered through a round-headed doorway of sixteenth-century date, and opposite it, in the south gable, a four-light traceried window of the same period survives, though it has been blocked internally by an eighteenth-century monument to John Burke of Glinsk. The Burke connection runs deeper still: set vertically into the wall at the south-east corner is an effigial tomb slab, a carved stone bearing a figure in relief, identified as belonging to a William Burke and dated to the fifteenth century. The slab attracted considerable scholarly attention in the early twentieth century, discussed by O'Flanagan, Knox, and Crawford in separate publications between 1902 and 1927. A carved cross and crucifixion scene formerly associated with the site has since been moved to a wall near the present Catholic church in Glinsk.

The ruins sit within the southern half of an early ecclesiastical enclosure, the kind of roughly circular or oval boundary that in Ireland often marks a monastic or church site of considerable age, pre-dating the Norman period and sometimes stretching back to the early medieval centuries. That wider enclosure gives the church a longer genealogy than its surviving stonework alone would suggest, layers of use compressed into a modest and rather battered rectangle of ground in north Galway.