The enclosing wall traces a gentle curve around the site, forming a rough circle roughly 55 metres across. That curve is not a casual accident of construction. Sub-circular enclosures of this kind are widely understood by archaeologists to be the footprint of early, pre-Norman ecclesiastical settlements in Ireland, where a founding community would define their sacred space with a curving boundary, a pattern that can predate the twelfth-century changes brought by the Normans by several centuries.

The wall itself dates to 1725, with repairs carried out around 1825, and an inscription once recorded on the gate-piers confirmed both dates, noting that the walls were rebuilt in 1725 and repaired one hundred years later. The church of St Mary, now disused, stands at the centre of the enclosure and was rebuilt in 1817, according to the same inscription. But the deeper history of the site only became clear through archaeological work carried out in 1998 and 1999. The 1998 assessment, conducted under licence number 98E0362, found a ditch running outside and concentric to the churchyard wall, along with two pits containing burnt material inside it, likely of medieval date. The following year, further excavation under licence 99E0305 uncovered a second ditch traversing the site from east to west. Archaeologists concluded that this outer ditch had probably served as an enclosing element around the medieval churchyard and had been deliberately infilled during the later medieval period. The present wall, it seems, may echo an even earlier inner enclosure, with the outer ditch representing a boundary that has long since vanished at ground level.

The graveyard is located in Crumlin village, close to St Agnes Road, in an area that retains just enough of its older character to make the site feel slightly out of step with its surroundings. The disused Church of Ireland building at its centre is not in regular use, so access to the interior of the church itself is unlikely, but the graveyard and its enclosing wall can be observed from outside. The rounded line of the wall is best appreciated by stepping back and looking at the overall plan, either on foot or by comparing the site against a map, where the sub-circular outline becomes immediately apparent.