Built in the late 14th century by Thomas Balbeyn, who was also known as “Cor”, this castle measured approximately 15.25 by 9.2 metres, placing it amongst the larger tower houses of its time. Various historical maps from the 16th and 17th centuries depict it differently; sometimes as a tall, thin tower with an attached lower portion bristling with cannon, other times as a round tower with a gabled roof, suggesting the structure may have evolved over time or been viewed from different perspectives by contemporary cartographers.

The castle’s history reads like a who’s who of Limerick society. After Thomas Balbeyn bequeathed it to the Corporation in his 1402 will, provided his brother Henry from Bristol didn’t fancy relocating to Ireland, the castle passed through numerous hands. During the Cromwellian period in the 1650s, Captain T. Holmes spent £70 repairing the structure, and by 1657 it had been transformed into what Dr. T. Arthur described as a “cytadle”, garrisoned by 200 men just two years later. The Hunt map suggests the castle featured an unusual two-door system, with one entrance leading to the ground floor whilst another provided direct access to the upper levels, a practical defensive feature common in Irish tower houses.

By 1696, however, Thom Cor Castle’s days were numbered. The city authorities ordered its demolition to make way for a market house, which was constructed on the site for the rather modest sum of £210. When archaeologist Brian Hodkinson conducted test trenching at the site in the late 1980s ahead of new development, he found no trace of the castle’s foundations, suggesting that the 17th-century demolition was thorough indeed. Today, nothing remains of this once-prominent landmark that appeared on every major map of Limerick for over a century, though its memory persists in the historical record as a testament to the ever-changing urban landscape of medieval Irish towns.