Known locally as both Fanning’s Castle and Whitamore’s Castle, the building takes its names from two prominent families who occupied it during the 17th century. The Fannings were in possession by 1641, whilst Francis Whitamore, who became mayor in 1682, ran what was considered one of the city’s finest inns from this location. The castle’s most famous resident was Dominic Fanning, who served as Mayor of Limerick from 1646 to 1652. After rejecting a peace treaty and leading the resistance against Oliver Cromwell’s son-in-law Henry Ireton, Fanning was executed at his own door in November 1651, and his home was subsequently demolished as punishment for his defiance.

Today, only portions of this five-storey tower house remain, with the south wall standing as the most intact element at approximately 11.5 metres high. Built from roughly coursed limestone with dressed quoins, the structure dates to around 1500 and originally fronted onto Mary Street. The building’s architectural features reveal its domestic nature; each floor contained splayed twin-light windows with window seats, and the east wall housed a large fireplace with a chimney flue running through multiple floors. Small wall cupboards and what appears to have been a spiral staircase in the thickness of the east wall speak to the practical considerations of medieval urban living. External corbels once supported wooden stairs or balconies that provided access between floors, though these timber elements have long since disappeared.

Archaeological surveys have revealed fascinating details about the tower’s construction and layout. The ground floor may have been barrel-vaulted, whilst the upper floors featured increasingly elaborate window designs, progressing from rectangular to ogee-headed openings. The fourth floor presents an unusual arrangement, with a stepped gable built against the inner face of the south wall, suggesting the roof rested at this level whilst the outer wall continued upward to form a defensive parapet. Conservation work was first undertaken by the state around 1940, and the building now stands as National Monument No. 383, a testament to Limerick’s medieval merchant class and the political upheavals of the 17th century.