Originally built by Henri de Londres, Archbishop of Dublin, the castle occupies a commanding position at the centre of a square-shaped motte on the western end of an east-west ridge. From this strategic vantage point, the fortress once overlooked the marshy river valley to the north, providing both defensive advantage and control over the surrounding landscape.

The surviving structure presents an intriguing puzzle for historians and archaeologists. What remains today includes portions of a projecting gate tower constructed from uncoursed rubble and part of a corner tower at the northeast angle. The castle sits atop a steep-sided motte surrounded by a wide, flat-bottomed fosse (defensive ditch), with traces of an external bank still visible on the northern side. The eastern wall of the stone castle rises from the base of the fosse all the way to the summit of the motte, where evidence of a possible window or doorway embrasure can be seen at its base. This arrangement, with the stone gatehouse protecting the entrance to the motte’s summit on the eastern side, mirrors the design of the Anglo-Norman castle at Newcastle in Wicklow.

The castle’s history extends beyond its initial construction, playing a role in the turbulent politics of medieval Ireland. In 1308, Piers Gaveston, the controversial favourite of Edward II, fortified Castle Kevin after successfully harassing and defeating the local Irish clans, the O’Byrnes and O’Tooles, in an effort to strengthen English control in the region. By the time of the Ordnance Survey in 1838-40, the castle was already in ruins; surveyors described it as a square mound about 12 metres high with masonry remains, surrounded by its deep ditch. Today, this monument is protected under a preservation order, ensuring that these evocative remnants of Anglo-Norman power continue to stand as witnesses to Ireland’s complex medieval past.