This imposing tower house, rising approximately 70 feet from its rocky foundation, was built by the Bourkes and later passed through various hands, including the O’Dalys and Lord Brittas. The castle’s name itself tells a story of disputed origins; whilst some claimed it meant “the O’Farrellys’ rock” (Carrigifarrioyla), historian John O’Donovan argued it derived from Carraig Fearghaill, meaning “Farrell’s Rock”. The structure appears on 17th century Down Survey maps and even merited a mention when the Earl of Sussex passed by in 1558, receiving refreshments from W. Burke.

The castle exemplifies classic Irish tower house architecture, measuring roughly 10.6 metres by 8.2 metres externally, with walls an impressive 6.5 feet thick. Built on a rock platform that drops sharply 6 metres on its western side, the location provided natural defensive advantages. Inside, the tower originally contained five storeys, with the fourth floor featuring a stone vault underneath. The internal dimensions, recorded as 19 feet 8 inches by 14.5 feet, housed various chambers including a spiral staircase tucked into the southwest corner, mural chambers above the entrance passage, and practical amenities such as a second storey fireplace and third storey latrine accessed from the staircase.

Archaeological surveys classify Carrigarreely as a Type 1A Tower House, characterised by its ground floor entrance leading to a lobby that cleverly divides access between the main chamber, a subsidiary chamber, and the corner spiral staircase. A later two storey range was added to the south side, taking advantage of the terrain’s 1.5 metre drop to align its upper floor with the tower’s lowest storey. Though time has taken its toll on the upper portions above the third storey vault, the castle retained much of its structure into the 19th century when the Ordnance Survey noted its walls were “perfect”, testament to the skill of its medieval builders.