The Castle of the Island of Kerry, as it was originally known, was built in 1226 by Geoffrey de Marisco, who served as Lord Justice of Ireland. The castle takes its name from its strategic position on what was then an island, Oileáin Ciarraighe in Irish, formed by diverting the River Mang around its walls into a defensive ditch complete with drawbridges and portcullises. Through marriage in the late 13th century, ownership passed to the powerful Fitzgerald family, the Earls of Desmond, for whom it became a crucial stronghold until its destruction during the wars of the 1600s.

Today, only fragments of this once extensive castle complex survive. The most substantial remains include a corner tower measuring roughly 4.7 metres by 4.57 metres and standing about 13.7 metres high, along with portions of the gateway tower that once housed two floors above its entrance. Victorian observers in 1841 noted walls up to 9 feet thick in places and described how the castle originally covered a square of about 200 yards. Another corner turret, described as resembling the tower house at Listowel, stands 60 metres from the main tower remains, though both structures are now in poor condition, overgrown with ivy and partially collapsed.

Archaeological investigations in the early 2000s revealed little beneath the surrounding ground, suggesting the castle’s footprint was largely confined to the surviving structures. Recent conservation work has highlighted just how precarious these remains have become; much of the stone has been robbed over the centuries, leaving some walls as thin as 15 centimetres in places. The castle that once commanded respect from English kings, evidenced by Henry III’s letter to its constable in 1231 following the death of William Marshal, Earl of Pembroke, now requires careful preservation to prevent its complete loss. Despite its ruinous state, these fragments continue to tell the story of medieval power struggles in Kerry, from its construction by an Anglo-Norman lord justice to its role as the chief seat of the rebellious Earls of Desmond, who were famously known as poets as well as warriors.