Built by the Barry family in the late 1200s, the fortress comprises a quadrangular ward roughly 62 metres north to south and 50 metres east to west, enclosed by seven-metre-high curtain walls. Four circular towers guard each corner, whilst rectangular towers project from the northern and western walls, and an elaborate gate tower dominates the southern approach. The castle’s rubble limestone construction features a distinctive low base batter, and whilst most of the structure stands to its full original height, only the southeast corner tower has succumbed to the centuries.

The gate tower itself reveals sophisticated defensive features typical of medieval engineering. Its entrance passage extends over ten metres through a barrel-vaulted tunnel, complete with recesses for both outer gates and a portcullis system. Above the passage, a series of mysterious rectangular shafts run obliquely through the vault; whilst their exact purpose remains unclear, they may have served as murder holes for defending against attackers below. The tower’s upper chambers, accessed via a spiral staircase in the northeast corner, showcase late-medieval additions including ogee-headed windows with decorated mullions. Two weathered sandstone heads, one possibly depicting an animal, still peer out from the tower’s southern face, though centuries of Irish weather have taken their toll on these curious decorative elements.

The castle passed to Sir Philip Percival in 1625, whose descendants held it for centuries, and it witnessed several battles during the turbulent 17th century. Each corner tower follows an identical design with three storeys, spiral staircases, and narrow arrow loops set in wide embrasures; the towers’ internal diameters range from three metres in the southwest to 3.75 metres in the northwest. The northern rectangular tower contains an enigmatic shaft running from ground to wall-walk level, possibly used for hoisting munitions or as a large latrine, though no exit chute exists. Beyond the walls, remnants of a fosse with an external bank on the north and west sides show where builders levelled the high ground to prepare the site. Now a National Monument under state guardianship, Liscarroll Castle stands as a remarkably complete example of Anglo-Norman fortification, its walls bearing witness to over seven centuries of Irish history.