Built in 1636 by the Archdeacon family, this imposing structure consists of a three-storey rectangular central block flanked by four-storey square towers at each corner. Though the floors and roof have long since collapsed, leaving the building in a dangerous state, the walls still stand to their full height, revealing the castle’s sophisticated defensive design. Multiple gun loops pierce the ground level walls, whilst elegant bartizans project from the outer corners of each tower, supported by five gracefully tapering corbels and topped with traces of stepped crenellations.

The castle’s architectural details speak to both its defensive purpose and the status of its builders. String courses run between floor levels on all elevations, whilst gables crown the main block and towers. The north wall features an impressive doorway with a cut-stone surround in two plain orders, topped by an elliptical arch and hood moulding, though this entrance is now blocked. Inside, where accessible, the layout mirrors that of Mount Long Castle, with corner towers containing single rooms at each level that open into the main chambers. The western wall showcases two remarkable fireplaces; the ground floor example features a simple elliptical arch, whilst the first-floor fireplace boasts an elaborate mantle with a three-tiered cornice and delicate branch and leaf carving on its console, beneath which the construction date of 1636 is carved in shallow relief.

The castle’s later history reflects the changing fortunes of such buildings in Ireland. Bernard Shaw undertook repairs and re-roofing in 1814, commemorated by his initials ‘B.S.’ carved above the first-floor fireplace. The British Army subsequently used it as a barracks, and Lord De Vesci made considerable additions in 1873. In 1908, the building found new life as the clubhouse for Monkstown Golf Club, who purchased it outright in 1959. However, when the club built new premises in 1971, the castle was abandoned once more, leaving this remarkable fortified house to deteriorate into its current precarious state.