When surveyed in 1840, locals noted that nothing remained visible of the castle itself, which once stood on a small hill about 100 metres in diameter and 15 metres high from the road level. The castle’s location can still be identified on historical maps, including a 17th century Down Survey map of Clanwilliam Barony that depicts it standing prominently on its hill, rendered as a tower house style fortification.

The castle’s documented history begins in 1242 when it was recorded as the manor of Tristellaueran. Throughout the medieval period, it passed through various hands of the powerful de Burgo (Burke) family. Walter de Burgo held it between 1272 and 1274, and by 1309, Richard de Burgo, Earl of Ulster, was paying fines on the manors of Esclon and Tristellauerans. The property continued through various Burke descendants; in 1410, Emon Burke, second son of Walter Duff Burke, received four seisreachs of Disert Labrais and four of Garran ui chiabaigh in the area. By 1641, Theobald Lord Brittas had settled the Castle of Grenanbeg, along with several other properties including Knockruo, Knocktanacastlane Castle, and Dunemona Castle, on his mother Margaret, widow of John Baron of Brittas.

The Civil Survey of 1654;56 provides one of the last detailed descriptions of the structure, recording that Lord Borke Baron of Brittas owned ‘a smale Castle in reparation and a marbell quarrie’ on the site. This suggests the castle was still somewhat functional in the mid;17th century, though already requiring repairs. The Down Survey terrier similarly noted that ‘There standes a Castle on the Lande of Insenlawrence’ belonging to Theobald Lord Brittas. By 1703, the estate was sold to the Hollow Blades Company as part of Lord Brittas’s holdings, marking the end of its long association with the Anglo;Norman nobility who had controlled this corner of Limerick for centuries.