The site features two distinct defensive lines positioned about 70 metres apart, creating a formidable barrier against any approaching threat from the mainland. The outer defences, which face inland to the north, consist of a rock-cut fosse varying between 2.5 and 6 metres deep and 6 metres wide. Along its inner edge runs a curtain wall that incorporates a central tower house and two smaller mural towers, one positioned halfway along each side. The inner defensive line faces south towards the sea, comprising another rock-cut fosse approximately 4 metres deep and 8 metres wide, backed by a slight earthen bank.

The three-storey tower house at the heart of the fortification stands largely intact, measuring 8.75 metres east to west and 6 metres north to south. Though its eastern wall doesn’t survive above the first floor, the remaining structure reveals sophisticated medieval architecture including a spiral staircase in the southeast corner, double-splayed windows, and a pointed vault over the first floor. The ground floor entrance, now blocked, sits near the eastern end of the south wall, whilst a second door immediately above provides access to the stairs. The second floor features window embrasures with stone seats in both the north and south walls, and evidence suggests a mural passage once connected the wall walks atop these walls through the thickness of the western wall.

Built by the de Courcey family, likely in the 15th century according to historical records, these fortifications may incorporate elements of an even earlier promontory fort. The two mural towers project about 1.2 metres beyond the curtain wall line; the western tower barely rises above ground level on the interior, whilst the eastern tower stands approximately 5 metres high externally and retains a lintelled window opening with a round-headed light. A modern road to the lighthouse now cuts through both defensive lines, with a recent gateway piercing the curtain wall immediately west of the tower house. The site has been protected under a preservation order since 1978, recognising its significance as one of Cork’s important medieval defensive structures.