This earthwork castle, dating from the medieval period, consists of a square earthen mound whose summit measures approximately 9 metres on each side and rises about 4 metres above the surrounding landscape. The motte’s distinctive square shape sets it apart from the more common circular examples found elsewhere in Ireland, suggesting either local building preferences or adaptation to the specific terrain.

Archaeological surveys have identified traces of a fosse, or defensive ditch, along the southern and western sides of the mound, though these features have been softened by centuries of weathering and agricultural activity. Such ditches were essential defensive elements, typically filled with water or left dry with sharpened stakes, creating an additional obstacle for any would-be attackers attempting to scale the motte’s steep sides.

This type of fortification represents the earliest phase of Anglo-Norman castle building in Ireland, introduced after the invasion of 1169. Mottes were relatively quick to construct, requiring mainly earth and timber, and served as strongholds from which the Normans could control newly conquered territories. The Kildellig example would originally have been crowned with a wooden palisade and tower, though no trace of these structures remains today. Its position in the landscape would have provided commanding views across the surrounding countryside, allowing its garrison to monitor local movements and assert Norman authority over the native Irish population.