The ruins sit on a south-facing slope overlooking a river valley, where only portions of the eastern and southern walls survive today. These remnants, built from roughly coursed red sandstone rubble, curve in a way that suggests the original structure may have been circular rather than rectangular; a distinctive architectural choice that would have set it apart from typical Irish tower houses of the period.

The castle’s history can be traced back to at least 1640, when Thomas Butler of Kilconnell held it as proprietor. By the time of the Civil Survey in 1654-6, it was already described as ‘the castle of Crohane with the walls standing onely’, indicating it had fallen into disrepair even then. When antiquarian Curry examined the ruins in 1840, he recorded considerably more substantial remains than what exists today: walls standing 20 feet high with evidence of a barrel vault that once supported the first floor. He measured the interior diameter at 21 feet 6 inches, with walls an impressive 9 feet thick; dimensions that speak to the defensive capabilities of this stronghold.

Since Curry’s visit, time has not been kind to Crohane Castle. Approximately 4 metres of wall height has been lost, the barrel vault has completely disappeared, and much of the stone facing has been robbed out for use elsewhere. What remains are wall fragments reaching just 2 metres in height, with a partially destroyed garderobe chute still visible in the external face of the eastern wall. The fragmentary nature of these ruins makes it impossible to definitively classify the castle’s original form, though the curved footings continue to hint at what would have been an unusual circular design in the Irish castellated landscape.