Snow covered the sports field at Byparken in January 2025 as archaeologist Arne Abel Stamnes and his colleagues followed the incoming data from a ground-penetrating radar (GPR) scanner.
As the equipment crossed the field in Roskilde, Denmark, shapes began appearing in the results, outlining parts of St. Clare’s Convent. Historians had assumed that little remained of the medieval complex after its demolition centuries earlier.
“This is the first time I have documented such a well‑preserved monastery complex with GPR, and in my assessment these are among the clearest GPR results from a monastery complex in Scandinavia,” Stamnes said in a press release.
The scans showed that substantial portions of the convent, which dates to 1256, survive about 3 feet (1 meter) underground.
Plans for Underground Parking Reveal a Medieval Monastery
Plans to construct an underground parking facility beneath the sports field prompted the investigation. Before the project proceeded, the museum organization ROMU wanted a clearer picture of what construction might encounter.
“We knew that St Clare’s Convent had been located here, but not how much of the complex from 1256 had been preserved. The GPR survey has produced very clear results and a solid basis for planning further investigations,” said archaeologist Jesper Langkilde in the press release.
Five monastic communities operated in medieval Roskilde, a center of religious and royal power. St. Clare’s was among them.
The Reformation brought the convent’s dissolution in the 16th century, followed by its demolition. Around half a million of its bricks were sold to Selsø Castle, strengthening the belief that little remained at the original site.
Because the present-day grass field had escaped later building construction, archaeologists could examine the site without first breaking the surface.
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Radar Maps the Buried Monastery
ROMU, the National Museum of Denmark, and the Norwegian Institute for Cultural Heritage Research (NIKU) collaborated on the survey. NIKU archaeologist Arne Abel Stamnes and Magnus Hjorth Jørgensen of the National Museum collected the radar data, which Stamnes later interpreted and processed.
The team drove an ATV-mounted scanner across the grass instead of opening trenches. The equipment sent electromagnetic waves into the soil and measured the returning signals. Changes in those signals allowed them to identify possible masonry, ditches, and other buried features.
The radar traced four wings surrounding a central cloister courtyard, including a church in the southern wing. The northern and eastern wings appear especially well preserved; in the east, the scans show room divisions and foundations for pillars that once supported vaulted ceilings. Other readings indicate that additional buildings may extend beyond the central monastery square.
NIKU building archaeologist and monastery expert Regin Meyer said the scans demonstrate how much researchers could still learn from the site.
“The dataset clearly shows the building‑archaeological potential that lies beneath the ground surface at this site. The material illustrates the valuable benefit of geophysical surveys for identifying and protecting building remains, and provides an exceptionally good basis for more precise archaeological investigations in the future,” he said
Trial Trenches Could Come Next
St. Clare’s is the last of Roskilde’s five known medieval monasteries to be located. The other four sites are protected, while St. Clare’s lacks that designation because authorities previously believed its remains had disappeared.
Roskilde municipality will decide whether archaeologists can dig trial trenches in the portion of the field proposed for the parking facility. The trenches could confirm what the radar detected, inform plans for a larger excavation, and help identify which sections of the convent require protection.
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Article Sources
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- This article references information from the NIKU: Thought the monastery was lost: Found the entire complex with ground‑penetrating radar under a football pitch