The structure, also known as Ballyhannanin, consists of a rectangular tower measuring approximately 11.4 metres by 8.5 metres externally, with walls that vary in thickness from 1.5 to 2 metres. Built from limestone with a rubble core, the tower originally rose to four storeys, though today only three remain intact; the fourth floor and its distinctive crenellated parapet have long since collapsed, leaving the structure open to the elements.

The tower’s defensive features tell the story of a turbulent past when such fortifications were essential for survival. A murder hole positioned above the entrance provided defenders with a strategic advantage, whilst the original oak door, reinforced with iron fittings, once secured the ground floor entrance. Inside, the tower reveals careful medieval craftsmanship, with a spiral staircase built into the thickness of the north wall connecting the various levels. Each floor served a distinct purpose, from storage spaces on the ground level to living quarters above, complete with window embrasures that provided both light and defensive positions.

Archaeological evidence suggests the tower house dates to the late medieval period, likely constructed in the 15th or 16th century when such structures proliferated across the Irish landscape. The surrounding area shows traces of an earlier settlement pattern, including what may have been a bawn wall that once enclosed the tower, creating a fortified compound typical of the period. Despite centuries of weathering and partial collapse, Castlefergus remains an evocative reminder of Clare’s medieval heritage, its limestone walls still commanding the landscape much as they did when first erected by long-forgotten lords.