The ruins of this 15th-century castle, a former stronghold of the O'Sullivan Beare clan, sit on a promontory overlooking the southern entrance to the sheltered harbour of Bere Haven, a fantastic spot for a summer picnic. The castle was destroyed by English forces during the Siege of Dunboy in 1602. Dunboy is at the end of a narrow road (the L8935), which leaves the main road 2.5km southwest of Castletownbere (parking space for two or three cars).
On the way to the castle, you pass the fenced-off shell of Puxley Mansion, a grand Victorian manor house that was once home to a copper-mining magnate and provided the inspiration for Clonmere in Daphne du Maurier's 1943 novel Hungry Hill. The manor was burnt out by the IRA in 1921; there have been attempts to restore it as a hotel, but it has lain abandoned since 2008.