The pointed arch is carved with roll and hood moulding, the kind of decorative stonework that speaks to serious ambition, and it terminates in a carved head, a detail easy to miss but striking once noticed. All the windows are now blocked, and the interior holds burials alongside a large tree that has taken firm root among the stones, lending the place the particular quality of somewhere that has been slowly surrendered to its own quiet processes.

This is a chantry chapel, a category of private religious building erected specifically to house prayers and masses for the souls of a founding family. According to researcher Michael Tutty, writing in 1979, it was apparently built by the Plunkett family in the sixteenth century. The Plunketts were among the more prominent Anglo-Norman dynasties of the Dublin and Meath region, and the quality of the stonework here reflects that standing. The chapel is modest in scale, roughly nine metres long and just under five metres wide, with walls approaching a metre thick. Inside the south wall sits an aumbry, a small recess built into the masonry to store sacred vessels, and a widely splayed window with chamfered limestone jambs that would once have drawn light across the interior. An L-shaped section of wall extends from the northeast angle of the building, and by the early nineteenth century a mausoleum had been added to the southeast corner, suggesting the site retained its function as a place of family burial well into later centuries.

The chapel sits within the broader cluster of medieval remains at St. Margaret's, a village a few kilometres north of Dublin Airport. The adjacent parish church is a separately recorded monument, and the two structures together give a reasonable sense of how a modest medieval settlement organised its religious life. Some rebuilding of the chapel walls has taken place at some point, so not everything visible is strictly sixteenth-century fabric. The elaborately carved doorway remains the most rewarding detail to examine closely, particularly the carved head at the termination of the hood moulding, which repays a careful look.