Storie & Archeostorie

A major medieval archaeological complex has been identified in Denmark, beneath the present-day Byparken area of Roskilde. Ground-penetrating radar surveys have revealed substantial remains of St Clara Convent (Sankt Clara Kloster), a medieval Franciscan nunnery whose surviving remains were previously thought to be largely lost.

The convent was founded in 1256 as a community of Poor Clares. Historical records indicate that the complex was destroyed by fire in 1302 and subsequently rebuilt. Following the Reformation, much of its land and property passed to the University of Copenhagen, while the convent buildings were gradually dismantled. Foundations and masonry were still visible in 1843, when the area was investigated.

Until now, however, the extent and preservation of the medieval architecture beneath the modern landscape remained uncertain.

A remarkably clear architectural plan

The investigation was undertaken by the museum organisation ROMU in cooperation with the National Museum of Denmark (Nationalmuseet), with the participation of Norwegian geophysicist and archaeologist Arne Abel Stamnes of the Norwegian Institute for Cultural Heritage Research (NIKU).

The team used Ground-Penetrating Radar (GPR), a non-invasive geophysical technique that detects buried structures by transmitting electromagnetic pulses into the ground and recording their reflections from subsurface boundaries.

The results revealed a substantial architectural complex approximately one metre below the present ground surface. The radar data show the outlines of rooms, columns, cloister walks and a church in the southern part of the complex.

The eastern wing is particularly well preserved. Its internal divisions are clearly visible, together with structures interpreted as vault-supporting piers. According to Stamnes, the clarity of the results is exceptional: the structures were sufficiently distinct to be recognised during the survey itself, making the site one of the clearest examples of a Scandinavian monastic complex identified through GPR.

What the geophysical survey can reveal

GPR works by transmitting electromagnetic waves into the ground. When the waves encounter materials with different physical properties, part of the signal is reflected back to the surface. These reflections can be processed to produce horizontal and vertical images of buried archaeological features.

At Roskilde, the method has made it possible to map a significant portion of the convent without immediately disturbing the archaeological deposits. The survey can indicate the location of buried structures with a reported precision of approximately 2-3 centimetres, providing valuable guidance for any subsequent archaeological excavation.

The technique does not replace excavation. Direct archaeological investigation remains necessary to establish the construction sequence, chronology, function and preservation of the individual structures detected by the radar.

A rare opportunity to study a medieval women’s religious community

St Clara was one of five medieval monasteries known from Roskilde, a city that played a major political and ecclesiastical role in medieval Denmark. Its cathedral, royal connections and numerous religious institutions made Roskilde one of the country’s most important medieval centres.

The rediscovered convent is particularly significant because it was a women’s religious institution. Archaeological excavations of medieval female convents remain relatively uncommon, and the surviving architecture may provide evidence for the spatial organisation of religious life, communal activities, everyday practices and material culture.

Unlike several other monastic sites in Roskilde, St Clara had not been protected as an archaeological monument because the convent was believed to have disappeared. The new geophysical evidence therefore substantially changes the archaeological assessment of the area.

Archaeology and a proposed car park

The discovery has immediate implications because Roskilde Municipality is considering the construction of an underground car park beneath the sports ground at Byparken.

ROMU is now discussing the next phase of investigation with the municipality and the Danish Agency for Culture and Palaces (Slots- og Kulturstyrelsen). Targeted archaeological test trenches could be opened within the area affected by the proposed development.

Combining excavation data with the GPR results would make it possible to verify the geophysical interpretations, assess the condition of the surviving masonry and establish the scope, cost and timetable of a potential archaeological excavation.

The authorities are also examining whether the best-preserved sections of the convent can be protected from the impact of future construction. The discovery therefore represents both a major opportunity for medieval archaeology and an immediate conservation challenge.