"Charles Fort (Irish: Dún Chathail) is a star fort located on the water's edge, at the southern end of the village of Summer Cove, on Kinsale harbour, County Cork, Ireland...

Charles Fort is built on the site of an earlier stronghold known as Ringcurran Castle, which featured prominently during the Siege of Kinsale in 1601. The fort, which is named after Charles II, was designed by the Surveyor-general Sir William Robinson - architect of the Royal Hospital Kilmainham. The fort was built in the 1670s and 1680s to a star fortification design - a layout specifically designed to resist attack by cannon.

The in-land bastions of the fort however are overlooked by higher ground, a fact of critical importance when the fort was besieged by John Churchill, 1st Duke of Marlborough (then 1st Earl) in 1690 during the Williamite War in Ireland. Repairs were made following the siege,and the fort remained in use as a British Army barracks for several hundred years afterwards...

The fort was relinquished by British forces following the Anglo-Irish Treaty, but it fell out of use after being burned by the retreating anti-Treaty forces during the Irish Civil War in 1922. The complex was named a National Monument of Ireland in 1971[4] and has been partly restored by Dúchas, the Irish heritage service." Source - Wikipedia