The site features two distinct lines of defence positioned about 70 metres apart. The outer defences, facing inland to the north, consist of a rock-cut fosse (a defensive ditch) ranging from 2.5 to 6 metres deep and 6 metres wide, with a curtain wall running along its inner edge. This wall incorporates a central tower house and two mural towers, one positioned halfway along each side. The inner defences face south and include another rock-cut fosse, approximately 4 metres deep and 8 metres wide, with a slight bank on its northern edge.

The three-storey tower house at the heart of the complex measures 8.75 metres east to west and 6 metres north to south, standing nearly to its full original height, though the eastern wall only survives to the first floor level. Access was originally through a lintelled doorway near the eastern end of the south wall, now blocked, with a spiral staircase in the southeast corner providing access to upper floors and the wall walk. The first floor features a pointed vault running east to west, whilst the second floor boasts lintelled window embrasures with stone seats in both the north and south walls. A clever architectural feature in the western wall includes a mural passage that once connected the wall walks atop the northern and southern walls.

The curtain wall, which probably once stood proud of the ground, now largely serves as a revetment along the inner edge of the fosse, showing evidence of multiple phases of rebuilding and repair. The two mural towers project about 1.2 metres beyond the curtain wall line; the western tower barely rises above ground level on the inside, whilst the eastern tower retains more of its structure, including a lintelled window opening with a round-headed light on its north wall. A modern roadway leading to the lighthouse now pierces both defensive lines, with a recent gateway cutting through the curtain wall immediately west of the tower house. The site, which may incorporate elements of an earlier promontory fort, has been subject to a preservation order since 1978, recognising its significance as one of Cork’s important medieval fortifications.