This substantial motte, designated as National Monument No. 545, is encircled by a deep defensive ditch, or fosse, which reaches depths of around five metres on the southwestern side and maintains a width of four metres. The monument’s defensive capabilities were further enhanced by what appears to be the remains of a square bailey on the northwest side, measuring approximately 32 metres on each side, with earthworks still visible at heights of up to two metres on the northern edge.

According to the Welsh chronicler Giraldus Cambrensis, this formidable earthwork was constructed in 1181, placing it firmly within the early period of Anglo-Norman expansion into Ireland. The motte and bailey design was a tried and tested fortification method brought over by the Norman invaders, allowing them to quickly establish defensible positions in newly conquered territories. These earthen castles could be erected relatively swiftly using local labour and materials, providing immediate military advantage whilst more permanent stone structures were planned or built elsewhere.

Adding an intriguing layer to the site’s history, a granite pillar standing 1.7 metres tall and decorated with a double-ended Latin cross in relief was discovered in the vicinity and has since been re-erected on the motte’s summit. This cross likely predates the Norman fortification and hints at earlier religious significance in the area, a common pattern where Norman builders appropriated existing sites of importance. Today, Castlemore Moat remains one of the finest examples of Norman military earthworks in the region, its steep sides and commanding presence still conveying the strategic importance it once held in medieval Carlow.