This National Monument (No. 351) takes the form of a rectangular courtyard fortress, measuring roughly 43 metres north to south and 46 metres east to west. The defensive walls, built from squared granite blocks in irregular courses, were once surrounded by a fosse, or defensive ditch, which archaeologists uncovered during excavations in 1955. What makes this castle particularly interesting is its relatively light fortification; unlike the heavily defended castles of the period, Ballyloughan’s curtain walls were surprisingly modest in their defensive capabilities.

The castle’s most impressive feature is its double-towered gatehouse, positioned at the centre of the southern wall. These twin circular towers rise three storeys high, flanking an arched entrance that would have controlled access to the inner court. The medieval builders incorporated clever defensive features including stairwells built within the wall thickness itself and machicolations at second floor level, allowing defenders to drop projectiles on attackers below. The fortress also features three corner towers: a low square tower on the northeast angle, which was later reimagined as a cottage during the eighteenth century; another small square tower on the southwest corner measuring 6 by 5.6 metres internally with two storeys, complete with intramural passages and chambers; and the foundations of a small square structure at the northwest angle.

Archaeological investigations, particularly those led by de Paor and published in the Journal of the Royal Society of Antiquaries of Ireland in 1962, have helped piece together the castle’s history and construction methods. The excavations revealed not only the defensive fosse but also provided insights into how this thirteenth-century fortress evolved over time, including its partial transformation during the Georgian period when practicality overtook military necessity.