This rectangular fortress, measuring roughly 10.7 metres by 8.8 metres, features walls nearly seven feet thick and was built in the distinctive Irish Gothic tower house tradition. The structure comprises five storeys with a vault over the fourth level, and its thick end wall cleverly incorporates a ground floor latrine, five upper chambers, and a sixth chamber ingeniously supported by an arch over the topmost principal room. Though local tradition in 1840 claimed it was built by the Danes and demolished by Cromwell, architectural evidence suggests it dates from the late fifteenth century, with some sources attributing its construction to the Earl of Desmond around 1306.

The castle's turbulent history reflects the broader conflicts that swept through medieval and early modern Ireland. In 1579, during the Desmond Rebellions, it was held by Irish and Spanish forces before falling to Sir Nicholas Malby, Governor of Connacht, following his victory at the third battle of nearby Monasteranenagh. The Earl of Desmond later complained that both the castle and town had been spoiled and important documents seized. By 1583, records describe it as "a large castle in parts ruinous, with a barbican, ruined on the north, and a courtyard, enclosed with a stone wall in great decay," though it still retained defensive features including an iron door. The fortress changed hands multiple times over the centuries; it was surrendered to Carew in 1600 by followers of the Sugan Earl, passed through the Casey family in the early 1600s, and eventually ended up in the possession of Sir Drury Wray before being forfeited and sold in 1703.

The site itself may have ancient significance predating the current structure. Some scholars suggest this could be the location of Aenagh beag, a fort and fair green claimed by the King of Cashel in 902 according to the Book of Rights. The area witnessed significant events including Turlough O'Brien's defeat of the Norse between 1148 and 1151, after which he founded Monasteranenagh Abbey nearby. By the mid-seventeenth century, the Civil Survey recorded the property as containing not just the castle but also a mill seat and ten cabins, indicating it remained a centre of local activity despite its partial ruination.