The watchtower is a post-medieval structure of the kind erected in the eighteenth and nineteenth centuries to deter body-snatchers from raiding fresh graves, a fairly grim but practical response to the demand for cadavers from anatomy schools. That it survives alongside the fragmentary east and west gable walls of a much older church, a roughly square granite baptismal font, and what was once a standing stone carved with concentric circles makes Cruagh graveyard an unusually layered site, even by Irish standards. The standing stone, recorded by researchers in the late nineteenth and early twentieth centuries, has since disappeared entirely.

The church's history reaches back well before any surviving stonework. Between 1179 and 1275 it was recorded as 'Ecclesia de Creuach' in the Crede Mihi, a medieval register of the diocese of Dublin, and it functioned as a rectory belonging to the monastic estate of Kilmainham Priory. The area fell within the English-controlled territory of the Harrold family, referred to in period documents as 'Harrold's Country'. When the priory's assets were dissolved in the sixteenth century, the tithes passed through several hands: in 1540 to 1541, one John Wyrall, a Dublin shoemaker, held them for 20 shillings per year, and in 1593 Queen Elizabeth granted a 21-year lease on the rectory to a John Lye. By 1615 the Royal Visitation of Dublin found a curate named Thomas Drakeshaw serving the church, though the building was noted as repaired but lacking books. By 1630, Archbishop Bulkeley's visitation recorded it as having been extinct since 1615. The place-name itself carries older layers still: the original Irish form, Craobhach, is associated in the Vita Tripartita with Dalua of Craoibech, said to have been of St Patrick's household and commemorated on 7 January.

The ruins sit in Cruagh graveyard off the Pine Forest Road, on a steep, grass-covered knoll with a retaining wall on the eastern side. What remains of the church amounts to two sections of gable wall, the eastern stretch built of roughly coursed granite boulders and still retaining an original window opening about 0.7 metres wide, the western section largely smothered in ivy. The granite font sits to the north of the main ruins. The graveyard is an active burial ground and the foundations of the church have been considerably disturbed by later interments. The Down Survey maps of the 1650s, held in the National Library of Ireland, show the church positioned near a branch of the Dodder, and the upland ground between two streams described in those maps is still recognisable today.