The rectangular structure, measuring roughly 13 by 10 metres, retains portions of its original walls; the north wall still reaches three metres in height, whilst the south and east walls survive to about half that. The western wall has been reduced to little more than a grass-covered mound, though evidence of a garderobe can still be spotted at its northern end. Inside the north wall, fragments of an inner wall mark where a mural staircase once spiralled upward through the stone fortress, and the entire site is encircled by low earthen banks whose origins remain unclear.

The castle appears on historical maps dating back to the 1650s, when it was marked on the Down Survey map of Moygoish barony in the townland of ‘Clunaby’, close to what the cartographers labelled Lough ‘Durzath’, now known as Derravaragh. At that time, the property belonged to Andrew Nugent, recorded as an ‘Irish Papist’ who owned 162 acres of arable land in the area. The Down Survey terrier for Street parish noted that by the mid-17th century there were already ‘two castles likewise at Clonaby’ amongst other ruinous fortifications in the parish, suggesting the structure had already seen better days even then.

By the 19th century, Ordnance Survey maps from 1837 still marked the site as ‘Castle’, acknowledging its historical significance despite its deteriorating condition. Today, visitors can reach the ruins via a boat quay situated 50 metres to the southwest, though they’ll need to navigate past bogland that extends 240 metres in the same direction. The base-batter visible in the remaining walls hints at the defensive architecture typical of Irish tower houses, built to withstand both siege and the passage of centuries.