St Fintan's in Sutton South, on the northern tip of the Howth Peninsula in County Dublin, measures just five metres long and two and a half metres wide internally, yet its walls contain a surprisingly dense record of architectural change, accumulated quietly over several centuries.

The building sits within a circular enclosure, a feature that often signals very early ecclesiastical origins in Ireland, pre-dating the formal parish structures introduced after the Norman arrival. The church itself appears to be Early Norman in construction, built from large blocks of sandstone, granite, and tufa, a lightweight volcanic stone sometimes used by medieval builders for its workability. The walls are battered, meaning they lean slightly inward as they rise, a technique that adds structural stability. The original entrance was a simple lintelled doorway on the west wall, later replaced by a pointed arch with chamfered jambs, a detail that places the alteration firmly in the later medieval period. Above the doorway, a square recess holds a circular ope, a small opening, and a single bellcote sits on the west gable. Inside, three wall presses are set into the walls, one of which, at the east end of the north wall, incorporates the arch of an earlier window that was simply absorbed into the later fabric. The south niche is angular in plan with deeply chamfered sides and a carved head, the kind of detail easy to miss in a dim interior. The east window, now blocked, once had a rounded arch with septfoil moulding and chamfered jambs of sandstone and limestone. Attached externally to the north facade is the Bellingham graveplot, enclosed within its own metal railings, a private burial enclosure of the sort occasionally associated with landed families.

The site is within a suburban setting in Sutton, and the church is secured with metal railings at the roof and door. Mortar has washed out of much of the exterior stonework on the south, north, and east walls, leaving the masonry exposed and the different stone types visible. Those interested in the carved head inside the south niche, or the absorbed window arch in the north wall, should look carefully once their eyes adjust to the interior light.