Look more carefully, though, and the ground begins to reveal its own much older geometry. The northern wall of the graveyard is not simply a boundary; it is the surviving remnant of an ancient inner bank, part of a substantial oval bivallate enclosure, meaning a site ringed by two concentric banks and ditches, that once stretched roughly 150 metres in its outer diameter. The outer bank, still around three metres wide, and its accompanying fosse, a shallow ditch that would originally have helped define and defend the perimeter, survive only on the northern side, curving quietly into the landscape beyond the modern boundary.

The graveyard sits on a site historically identified as Derrylossary church, a medieval ecclesiastical foundation whose standing was significant enough to warrant a place within the administrative structure of St Patrick's Cathedral in Dublin. At some point, the archbishop of Dublin granted it to the prebend of the cathedral's Chancellor, a form of ecclesiastical benefice that provided income to a cathedral officer. No trace of the original church survives above ground today, though the presence of bullaun stones, granite boulders with one or more cup-shaped hollows worn or carved into their surface and commonly associated with early Christian and pre-Christian sacred sites, suggests the site carries layers of use stretching back well before the medieval period. Three bullaun stones have been recorded within the enclosure: one inside the graveyard, one just outside the western wall, and a third roughly fifteen metres to the northeast of the graveyard wall. Price and Stephens, writing in 1948, also noted a fourth example approximately 200 metres to the northwest, a stone later located by archaeologist Chris Corlett in 2005.

The bullaun stones are scattered enough that a visitor wandering only within the graveyard proper might easily miss the ones outside the walls. The earthworks of the enclosure are subtle, most legible from the northern side where bank and fosse remain intact, and worth examining slowly rather than in passing.