Somewhere in the small north County Dublin village of Garristown, a medieval castle once stood, and despite the survival of documentary records that prove its existence, its precise location has never been identified. What remains is a puzzle in the landscape, a structure reduced to ambiguity, known only through a mid-seventeenth-century snapshot and one possible fragment of carved stone.

The evidence comes from the 1654 to 1656 Civil Survey of Dublin, a Cromwellian-era land assessment compiled in the aftermath of the Confederate Wars. The survey recorded that in Garristown, on the lands of Elizabeth Talbot, widow of John Talbot of Malahide, there stood a ruined castle alongside a thatched stone house known locally as the College of Garristown, a garden plot, twenty-three tenements, a mill, a few ash trees, and a parish church. The entire complex was valued by the jury at one hundred pounds, with the mill separately assessed at three pounds per annum. The survey notes that the premises constituted a Manor and had kept both a Court Leet and a Court Baron, the two main forms of manorial jurisdiction in medieval Ireland. These courts would have managed local tenancy disputes and enforced the customs of the estate. The Talbot family, one of the most prominent Anglo-Norman dynasties in the Dublin area, had their principal seat at Malahide, and Elizabeth appears as the surviving holder of these Garristown lands at the time of the survey.

The only physical candidate for a remnant of the castle is a limestone hood moulding fragment, a decorative arched surround typically used above windows or doorways, now embedded in the south gable wall of a two-storey building directly opposite Garristown Church. It may have originated from the castle, though no firm connection has been established. The building itself is not open to visitors, but the fragment is visible from the road. Anyone passing through the village looking for traces of its manorial past will find the church nearby and, across from it, this single repurposed stone, quietly holding its ambiguous place in a wall.