Built around 1214 by Henri de Londres, Archbishop of Dublin, this Anglo-Norman fortification played a crucial role in medieval Ireland’s tumultuous politics. The castle’s strategic position allowed its occupiers to control the surrounding valleys and monitor movements through this part of the Wicklow Mountains, making it a valuable asset in the ongoing struggles between the English administration and the Irish clans of the region.

The site underwent significant changes throughout its history, most notably in 1308 when Piers Gaveston, Edward II’s controversial favourite, fortified and likely enlarged the castle after defeating the local O’Byrnes and O’Tooles clans. Today’s remains reveal an almost square motte measuring 70 metres north to south and 46 metres east to west, with a level summit rising six to seven metres above the surrounding fosse. The motte’s steep sides are faced with uncoursed rubble, and the entire structure is encircled by a flat-bottomed defensive ditch, six to eight metres wide. To the east, a possible bailey area extends for 143 metres, though its exact boundaries remain uncertain due to the natural topography of the narrow ridge.

By the time the Ordnance Survey documented the site in 1838-40, Castle Kevin was already a ruin, described as a square mound about 40 feet high with visible masonry remains surrounded by a deep ditch. The castle had been granted to the O’Tooles at some point but was destroyed before 1636 and never rebuilt. Archaeological investigations have revealed additional features including a sunken road running along the base of the ridge and outer defensive banks, particularly visible on the northern side. The monument has been protected under a preservation order since 1940, recognising its importance as a well-preserved example of Anglo-Norman military architecture adapted and reused throughout centuries of conflict in medieval Ireland.