 In the late 16th century, the citizens of Cork appealed to Queen Elizabeth I to construct a fort at Blackrock to "repel pirates and other invaders".In 1582 a fortification was built on the site, and later around 1600, a round tower was constructed to safeguard against pirates "carrying away" vessels entering the harbour.The earliest elements of this structure remaining today are a circular tower on the water's edge, 10.5m in diameter, with walls 2.2m thick.