This four-storey rectangular tower house, measuring 12 metres by 10 metres, belonged to the O’Ryan family according to historical records from 1893. The castle appears on the Down Survey maps of 1655-6, both for the barony of Gowran and the parish of Ullard, though curiously it’s absent from the accompanying terrier. What the documents do reveal is that by 1640, the lands of Cloghasty and nearby Knockbarron were held by a mix of proprietors including the Earl of Ormond and several members of the Ryan family; Teige Ryan, Edmond Ryan, and Teige Baccagh Ryan, all noted as Irish Catholics.

Today, the castle stands as a romantic ruin, its sandstone rubble walls clothed in ivy and the interior completely overtaken by vegetation. The structure shows the typical defensive features of its era, including a pronounced base batter rising to 1.6 metres and walls built from roughly coursed local sandstone with larger, carefully cut blocks forming the corners. The southeast and northeast walls remain the best preserved sections, with the southeast wall still displaying a rectangular loop window at first floor level and traces of what would have been the wall walk at parapet height.

While much of the castle has succumbed to centuries of neglect, with the northwest and southwest walls reduced to mere stumps of about a metre high, enough remains to appreciate its former strength. A fireplace in the southeast wall at ground level appears to be a later addition, perhaps added when the castle’s military importance had waned and comfort became more of a priority than defence. The eastern end of the southeast wall shows evidence of robbing, where stones have been removed over time, likely repurposed for local building projects in the centuries since the castle fell from use.