The castle’s story begins in 1610 when the lands were granted to James, son of Archbishop Myler McGrath. The following year, Carew recorded that the Archbishop of Cashel had begun building what he called “a prittie castle” at Termon McGrath, with plans to quickly finish both the castle and its protective bawn wall. This ambitious project would create one of the most defensively sophisticated tower houses in the region, though its active life would prove relatively short; Cromwellian troops bombarded the castle during their 1649-50 campaign, destroying the north wall and leaving it in ruins ever since.

The five-storey tower house measures 11.22m by 9.02m externally and showcases impressive defensive architecture that reveals the uncertain times in which it was built. Its entrance, positioned at ground level on the east wall, featured multiple security measures including internal door rebates, an external hinged iron grille secured by chain, and a gun loop at the apex for protection from above. Beyond the entrance, a small mural lobby with a murder hole provided another layer of defence. The ground floor bristled with six rectangular horizontal windows that doubled as gun loops, whilst the spiral staircase in the northeast corner could be sealed off at multiple levels. Each floor served different purposes; the second floor housed the main living quarters with large mullioned windows and a central fireplace, whilst the third floor contained similar amenities including a transomed window and another fireplace. The defensive features extended to the roof, where a battlemented parapet protected the wall walk, complete with a bartizan at the southeast corner and machicolations along the west face.

The castle’s L-shaped bawn wall, measuring approximately 27m square, created a fortified courtyard protected by circular two-storey towers at the northeast and northwest corners. These towers, accessed through lintelled doorways with drawbar holes, contained gun loops on both levels. The east wall alone preserved evidence of seven gun loops, whilst traces of a shallow fosse outside suggest additional defensive earthworks. Archaeological evidence indicates a small building once stood within the bawn near the south end of the west wall, and foundations of a central gate in the north wall connect to a 4.3m wide road that extends northward for about 100m. The Down Survey map of 1655-6 marks the site as “Tarmon McGragh Castle & Towne,” suggesting a small village once clustered around this formidable stronghold, though today only the castle’s weathered stones remain to tell its tale.