The Down Survey maps from 1655-6 show a castle standing here, though the fortification itself has long since vanished. What remains today is an eighteenth-century house that tells only part of the story; beneath it lie extensive cellars that predate the current building and have no structural relationship to it whatsoever.

These mysterious cellars likely represent the last physical traces of the medieval castle that once commanded this spot. The Down Survey, commissioned by Oliver Cromwell to map Ireland following his conquest, captured the castle at a pivotal moment in Irish history, just before many such structures fell into ruin or were deliberately demolished. The survey’s cartographers recorded thousands of castles, churches, and settlements across Ireland, creating an invaluable snapshot of the landscape before centuries of change transformed it.

Today’s Johnstown House presents a genteel Georgian face to the world, but those underground chambers hint at its more turbulent past. The disconnect between the cellars and the house above suggests that when the eighteenth-century builders arrived, they simply constructed their new mansion atop the foundations of the old castle, incorporating what they could use and leaving the rest buried beneath. It’s a common story across Ireland, where elegant country houses often conceal medieval bones in their basements, each layer of construction marking a different chapter in the long, complex narrative of Irish history.