Known as Grania Wael’s Castle, this National Monument dates from the early to mid-sixteenth century, though historical records are frustratingly sparse. The castle first appears in a 1574 list of O’Malley strongholds, and by the 1750s it had fallen into ruin. Its fortunes changed in 1826 when Sir S. O’Malley, then owner of the island, restored the building for use as a police barracks; a dual purpose reflected in early Ordnance Survey maps labelling it as both castle and police station.

The tower house forms an irregular rectangle measuring roughly 10 by 8 metres at ground level, with distinctive bartizans projecting from the northeast and southwest corners. These defensive features, each supported by five massive corbels and now weatherproofed with small slates, suggest a relatively late medieval construction. The original entrance near the north end of the east wall leads through a lobby to a narrow mural staircase, though much of the original stonework was stripped away during nineteenth-century renovations. The ground floor chamber features opposed arrow loops with pointed arched embrasures, whilst the first floor served as the main living quarters, complete with access to the bartizan chambers and a garderobe in the northwest corner.

Despite extensive nineteenth-century alterations that saw the removal of nearly all original doors and windows, the castle retains fascinating medieval details. The walls show evidence of generous plastering and limewashing over the centuries, whilst drainage holes in the parapet base suggest the original roof was hipped in the medieval manner. The second floor, accessed via stairs through the south wall, would have provided additional living space, though only the joist holes from the Victorian floor remain. Today, visitors can still trace the building’s defensive layout; from the bartizans that once allowed defenders to cover the walls with crossfire, to the thick walls that taper outward from first-floor level, creating the characteristic batter of Irish tower houses.