Located roughly halfway between Ballyvaughan and Black Head, about 60 metres from a raised shingle beach, this four-storey limestone fortress was home to various occupants for nearly 300 years. The L-shaped structure, measuring 8.7 metres east to west and 6.9 metres north to south, features a protruding stair tower at its southeast corner and has been carefully conserved by the Office of Public Works as National Monument number 509.

The castle’s history reflects the turbulent nature of Irish land tenure during and after the Tudor conquest. Though primarily associated with the O’Loughlin family from 1574 onwards, the earliest records show King Henry VIII granting Gleninagh to Richard Harding in 1544. The lands later passed to the see of Kilfenora in the early 17th century, and during Cromwell’s campaign in 1650, Murrough O’Brien sailed into exile from this very spot. The O’Loughlins eventually regained possession and remained until the 19th century, when Ordnance Survey letters noted the castle was still “in good repair and thatched with straw which gives it rather a homely appearance.”

Built from coursed limestone blocks with a slight base batter, the castle demonstrates both defensive ingenuity and domestic comfort. Its rounded corner bartizans, each fitted with five circular pistol loops, provided defence at the upper levels, whilst a box machicolation protected the pointed entrance doorway in the western wall of the stair tower. Inside, the barrel-vaulted ground floor chamber leads up through multiple levels, each with distinctive features: cupboards built into walls, garderobes with chutes, and various window styles from simple slits to two-light ogee-headed openings. The 17th-century modifications, including the addition of an attic level with chimney stacks and rectangular windows with hood mouldings, show how the castle evolved from military stronghold to comfortable residence. Today, visitors can still trace the foundations of a possible bawn wall immediately west of the tower, whilst nearby archaeological features including Tobernacrovaneeve holy well, Gleninagh church and graveyard, and several fulacht fia sites provide context for centuries of continuous occupation at this atmospheric coastal location.