Derry Round Tower

A Medieval Monument Rediscovered

For centuries, the Derry Round Tower lay hidden in plain sight, mistaken for the ruins of a 17th-century windmill. Located on the grounds of Lumen Christi College grammar school at 10 Cooke Street, this remarkable structure was scientifically dated to the 13th or 14th century through innovative radiocarbon analysis of mortar samples collected during conservation work in 2013. Researchers from Queen's University Belfast and local historians from the Derry Tower Heritage Group confirmed what had long been suspected: this was no windmill, but a genuine medieval monastic bell tower—the only medieval structure still standing within Derry's city boundaries.

Symbol of Monastic Power and Prestige

Irish round towers, known as cloigtheach in the Irish language, served primarily as bell towers for monastic communities. However, they represented far more than functional architecture. These distinctive structures were symbols of a monastery's power, wealth, and spiritual importance. The presence of a round tower in Derry indicates the exceptional significance of St Columba's monastery in the north-west of Ireland during the medieval period. Of approximately 90 known round towers in Ireland, the Derry example is unique in its urban setting and its survival through centuries of urban development.

From Bell Tower to Windmill

Historical maps from 1600 show the round tower standing in this location. By 1685, however, the structure no longer appeared on maps, replaced instead by references to a windmill on the city's outskirts. Rather than being demolished, the tower's sturdy base was ingeniously repurposed by 17th-century builders who adapted the medieval stump for their new structure. This practical reuse allowed the ancient monument to survive when all other medieval buildings in Derry were demolished or buried beneath centuries of urban construction and development.

Archaeological Significance and Urban Context

Dr Colm Donnelly, Director of the Centre for Archaeological Fieldwork at Queen's University Belfast, emphasised the tower's exceptional importance: "This monument is the only medieval structure still standing in Derry. All other medieval buildings that were once here are now gone, buried under the centuries of building activity that have happened in the city over the past 400 years." The tower's survival makes it an irreplaceable window into Derry's medieval past and its role as a major ecclesiastical centre.

The Discovery Process

The rediscovery of the tower's true age was made possible through cutting-edge radiocarbon dating techniques developed at the 14CHRONO Centre for Climate, the Environment, and Chronology at Queen's University Belfast. This method measures carbon-14 trapped in mortar when lime originally set, allowing researchers to date the building fabric directly. The Derry Tower Heritage Group's five-year study and their foresight in preserving mortar samples during earlier conservation work proved instrumental in confirming the tower's medieval origins.