Dunseverick Castle is located on the peninsula near the small village of Dunseverick and the Giant's Causeway.
Saint Patrick is recorded as having visited Dunseverick castle in the 5th century AD, where he baptized Olcán, a local man who later became a Bishop of Ireland. The original stone fort that occupied the position was attacked by Viking raiders in 870 AD.
In the later part of the 6th century AD, this was the seat of Fergus Mor MacEirc (Fergus the Great). Fergus was King of Dalriada and great-uncle of the High King of Ireland, Muirceartaigh (Murtagh) MacEirc. It is the 500 AD departure point from Ireland of the Lia Fail or coronation stone. Murtagh loaned it to Fergus for the latter's coronation in western Scotland part of which Fergus had settled as his sea-kingdom expanded.
The O'Cahan family held it from circa 1000 AD to circa 1320 AD, then regained it in the mid-16th century. Last one to have the castle was Giolla Dubh Ó Catháin, who left it in 1657 to settle in the Craig/Lisbellanagroagh area. Post 1660 they use the anglicised name McCain/O'Kane.
The castle was captured and destroyed by General Robert Munro in 1642 and his Cromwellian troops in the 1650s, and today only the ruins of the gatelodge remain. A small residential tower survived until 1978 when it eventually surrendered to the sea below.
References:Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).