The castle, once known as Cathair Conchubhair (the Castle of Cahir Conor), was built atop a cashel; a stone ringfort that itself was constructed on an earlier crannóg, or artificial island. Today, the main surviving structure is a four-storey rectangular tower house measuring roughly 7.5 metres north to south and 6 metres east to west, with walls 1.5 metres thick. Though the tower still stands, access is currently restricted by a padlocked gate, and the structure shows signs of both decay and modern intervention, with cement repointing and rebuilt battlements using limestone rubble rather than the original sandstone.

The tower house features several defensive and architectural elements typical of its era, including a barrel vault over the second floor, a now-destroyed doorway in the north wall, and mural stairs built into the eastern wall. A circular bawn wall, essentially a defensive courtyard wall, curves from the northeast to southeast corners of the tower, following the line of the earlier cashel beneath it. The contrast between building phases is visible in the stonework; the ancient cashel consists of uncoursed cyclopean masonry, whilst the later medieval structures employ mortared, coursed walls. Just three metres west of the tower, ivy-covered foundations mark the remains of a rectangular house, likely the thatched dwelling mentioned in the 1640 Civil Survey, which described the property as “a little castle with a little Bawne aboute it in an Island in ye Shannon, it wants repayre & a thatcht house within the Bawne.”

Historical records trace the castle’s ownership through various branches of the O’Brien dynasty, with Tadhg O’Brien of Adare listed as proprietor in 1640. The site appears on the Down Survey map of 1654-7, documenting its significance in the local landscape during that turbulent period of Irish history. The castle’s connection to Murchartach O’Brien of Ara, Bishop of Killaloe from 1570 to 1613, is documented in contemporary deeds, placing it firmly within the complex web of Gaelic lordship and ecclesiastical power that characterised North Tipperary in the late medieval and early modern periods. Since 2001, the monument has been protected by a preservation order under the National Monuments Acts.