Also known as Caisleán Bhun Inbhir or Bunaneer Castle, this fortified residence has been attributed to both the O'Sullivan Mores and the Brennans, though its exact origins remain somewhat murky. What is certain is that the castle witnessed action during the turbulent 1640s, when O'Sullivan More's forces clashed with Cromwellian troops in the nearby field of Droumfaddy in 1641.

The rectangular tower house, measuring roughly 12 by 10 metres, was constructed from split stone rubble bonded with mortar that contains beach pebbles and marine shells; a reminder of its coastal setting. Originally rising three storeys, only two floors now remain, with the south wall and southwest corner having collapsed over the centuries. The building's defensive features are particularly noteworthy, including triangular recesses on each wall face that likely housed gun loops to protect the base of the castle, and a murder hole above the entrance lobby through which defenders could attack unwelcome visitors. The ground floor entrance, located midway along the western wall, may have been secured by an iron grille operated by chains from within.

Inside, the castle follows a typical tower house layout with a main chamber on each floor and smaller mural chambers tucked into the thick walls. A spiral staircase in the northwest corner provided access between levels, whilst ogee and round headed windows with limestone dressings brought light into the dim interior. The first floor boasted a broad fireplace and what appears to have been comfortable living quarters, complete with a garderobe whose chute discharged through the eastern wall. Though time has taken its toll on this coastal stronghold, enough remains to paint a vivid picture of life in a 16th or 17th century Irish tower house, where comfort and defence went hand in hand.