The west entrance to this ruined medieval church in Palmerstown Lower has inclined jambs, meaning the sides of the doorframe lean slightly inward rather than rising vertically, a feature associated with pre-Norman construction in Ireland. Somebody, at a later point, inserted a round-headed window above or nearby, and a featureless window was pushed into the south wall at a different period again. The building you see today is not the product of a single moment but of several centuries of use, adaptation, and quiet accumulation.

The church sits off Mill Lane on a natural shelf above the River Liffey, a position that gives it a slightly elevated, considered quality. By the twelfth century it was held by the Fratres Cruciferi, a religious order of canons also known as the Crutched Friars, who followed an Augustinian rule and were associated with hospital care and pilgrimage routes across medieval Europe. The fabric of the building reflects that long arc of occupation. The nave measures roughly nine metres by five, built from large blocks of randomly coursed masonry, and is lit on the north side by a double-light window with chamfered jambs and traces of careful drafting in the stonework. The chancel, entered through an arch rising from squared imposts and carrying some moulding, is smaller and more considered in its proportions. Its east window was originally pointed, though the mullion is now missing. The walls survive to the eaves, the gables remain steeply pitched, and a belfry sits over the west gable, giving the whole structure a completeness that many ruins of comparable age have lost.

The site is reached via Mill Lane and the church occupies its shelf above the Liffey with some discretion; it does not announce itself from any great distance. The NW-SE alignment is slightly irregular by ecclesiastical convention, which may itself be a clue to the building's pre-Norman origins. Anyone with an interest in early Irish church architecture will find the doorway jambs and the layering of inserted windows worth examining closely, as they condense several phases of building activity into a relatively compact structure. The stonework repays slow attention rather than a quick circuit.