The castle, which belonged to this prominent Gaelic clan, originally featured a substantial square tower measuring approximately 32 feet by 28 feet and standing about 20 feet high. According to historical records from 1907, this ancient tower was eventually incorporated into a later house, creating an unusual blend of medieval fortification and more recent domestic architecture.

The house itself was abandoned around 1870, marking the end of centuries of occupation at this site. Since then, the building has been completely demolished, leaving no visible trace of either the original tower or the later residence that engulfed it. The complete disappearance of these structures means that visitors to Coolmain Bay today will find only an empty site where this piece of Mac Carthy history once stood.

The Mac Carthy Riabhach, or “Grey Mac Carthys”, were an important branch of the Mac Carthy dynasty who controlled significant territories in Cork. Their castle at Coolmain would have served as both a defensive position overlooking the bay and a symbol of their authority in the region. While the physical structure has vanished, the site remains significant to understanding the medieval landscape of West Cork and the territorial divisions among the Gaelic lordships that once dominated this corner of Ireland.