The historic monument of Cromwell’s fort on Inishbofin lies in ruin on the eastern entrance into Inishbofin harbour. Believed to have been built on the previous site of (Don) Bosco’s castle in 1656, a supposed ally of pirate queen Granuaile, this bastioned fort was constructed using local stone. The harbour would trap ships looking for safe haven from the wild Atlantic Ocean and would be raided by enemies stretching a chain across the harbour and charging by horse, cutting down the ships and their masts, leaving them vulnerable to Cromwell’s followers.