Where once a formidable stronghold commanded views across the river valley to the north and east from its prominent rock outcrop, today only fragments of limestone walls and a quarried depression mark its location. The castle’s demise was hastened by quarrying activities that literally undermined its foundations, though even before this industrial intervention, the structure was already in decline.

Historical records paint a picture of the castle in its better days. The Civil Survey of 1654-6 reveals that James, Lord Baron of Dunboyne, an Irish Catholic, owned the manor, castle, town and lands of Drangan in 1640, though his mother Ellen, Lady Dowager of Dunboyne, actually occupied the property. At that time, the estate boasted not only the principal castle but also a slate-roofed mansion house, a smaller thatched castle structure, and various other buildings within a defensive bawn wall. The Butlers, particularly the Dunboyne branch of that influential family, maintained their connection to the castle into the early 1700s, with Colonel Butler recorded as its last resident.

By the time the Ordnance Survey team arrived in the early 1840s, they found merely a single eastern wall standing about 10.6 metres high and 1.8 metres thick, built of well-grouted limestone. Even then, the foundations of the other walls had vanished, making it impossible to determine the castle’s original dimensions. This last substantial remnant fell around 1840, according to local historian Brennan, leaving only the fragmentary walls visible today; roughly coursed limestone sections bonded with lime mortar that may have formed part of the castle complex or its protective bawn. Some of the castle’s dressed stones likely found new purpose as headstones in the nearby medieval church graveyard at Drangan, about 160 metres to the south-southwest, where these repurposed drainage stones still stand.