Today, little more than a pile of rubble marks the spot where this substantial structure once stood, though archaeological evidence suggests it stretched approximately 20 metres from east to west. The castle was erected by the Dunne family, with historical records offering conflicting dates; one source places its construction in 1427, whilst the O’Doyne Manuscript attributes the building to Tadhg Mac Laighnigh Ui Duinn in 1475.

The castle sat within an impressive defensive system that included a bawn wall, traces of which remain to the south, accompanied by a ditch on the eastern and southern sides. The entire complex appears to have been positioned at the centre of a large circular enclosure, defined by an earth and stone bank with an outer fosse and an entrance gap facing west. This ringwork likely formed the earthen foundations for the bawn wall that protected the castle and its extensive grounds.

By 1608, the site had developed into a thriving estate, complete with a hall, parlour, kitchen, brewhouse, and bakehouse within the bawn, alongside gardens, an orchard, a park, stables, cattle houses, and tenant accommodations spread across the northern and western portions of Castlebrack town. The castle’s military significance continued into the 17th century; it was captured and partially dismantled by Colonel Hewson in 1653, repaired and fortified with extensive outworks by Colonel Terence O’Dunne in 1680 in preparation for the Williamite wars, and finally fell into permanent ruin around 1691. Its last known inhabitant was reportedly a Colonel Dunne, marking the end of the family’s long association with this once stately stronghold.