A medieval castle has been discovered inside a university building in Dublin

Significant sections of the early 13th-century Norman castle have been preserved within the building of University College Dublin. According to the university, the medieval walls and other architectural features of Rowback Castle lie hidden beneath the plaster of the building, which from the outside appears predominantly Victorian.

It was previously thought that the dilapidated castle had been dismantled during the redevelopment of the estate. Research by Tadg O’Keeffe, a historian of medieval architecture, shows that builders of the Georgian and Victorian eras did not destroy the old walls, but incorporated them into the new building.

Details

Rowback Castle stood on one of the routes to medieval Dublin and served as a fortified outpost. Historical sources indicate that it was built shortly after the Norman invasion of Ireland, which began in 1169, and was subsequently rebuilt on several occasions.

O’Kiff uncovered surviving stonework and other medieval features beneath the later plasterwork. He estimates that the oldest parts date back to the early 13th century. If the dating is correct, Rowback could turn out to be the oldest surviving building on a university campus in Ireland.

Traces of the castle have survived not only in the walls. The current courtyard behind the building, the researcher concluded, corresponds to the medieval inner courtyard. Thus, later alterations concealed the old structure but did not completely alter its layout.

Watercolours by the artist Gabriel Béranger helped to shed light on the building’s history. Around 1765, he sketched the ruins of Rowback from several angles. The images reveal not only the general outline but also small architectural details which have been successfully matched with features of the present-day building.

By the 18th century, the castle had already fallen into ruin. Subsequent owners modernised the estate, and researchers long assumed that the medieval structure had been demolished and the stone reused. This is precisely how many castles in the southern part of Dublin disappeared, particularly in the 17th century.

Historical sources name one of the medieval Lord Chancellors of Ireland amongst Roebuck’s former inhabitants. According to local tradition, the deposed English and Irish King James II may have stayed here in 1689; however, this account is based on legend and is not considered a firmly established fact.

The findings of the architectural and historical study have been published in the journal *Archaeology Ireland*. The university’s press release makes no mention of large-scale excavations: the discovery stems primarily from a reassessment of the existing building, an analysis of its structure and a comparison with historical depictions.

Why this is important

The castle was not found underground — it had remained part of the existing university building all along. This case demonstrates that later finishes can conceal much older structures, even in places where the site has been repeatedly studied and used.

For the history of South Dublin, the discovery is particularly valuable due to the poor state of preservation of the region’s medieval fortifications. Many castles were dismantled, and their stone was reused in the construction of more practical houses; consequently, along with the walls, knowledge of the layout, building techniques and the development of the suburbs was lost.

The surviving parts of Rowback allow us to study how the Norman fortress changed during the Middle Ages and was subsequently adapted to the requirements of 18th- and 19th-century manor house architecture. The building has become a physical chronicle of several overlapping eras.

Consequently, conclusions regarding the site’s age and status are based on architectural analysis, historical sources and drawings. Further investigations of the masonry and documentation of concealed elements may be required to clarify the construction phases. The statement regarding the oldest building on the university campus should therefore be regarded as a well-founded assessment rather than a definitively settled matter.

Source

Lost medieval castle found hiding inside UCD building. University College Dublin, 18 September 2026. Professor Tadga O’Keeffe’s research was published in the journal *Archaeology Ireland*.

Further context: Lost medieval castle found hiding inside university building in Dublin, Phys.org, 18 September 2026.