Archaeologists dig for clues to Turku’s origins at medieval bishop’s estate

Excavations are underway at the historic Koroinen peninsula near Turku to uncover new details about Finland’s earliest ecclesiastical centre, a site long overshadowed by its more studied neighbour, the medieval bishop’s church.

Around 20 archaeology enthusiasts from Finland, Sweden, and the UK are participating in the two-week dig, timed to coincide with Turku’s 800th-anniversary celebrations. Led by the University of Turku, the project targets the bishop’s manor—an area that has received far less attention than the adjacent church ruins, despite its central role in medieval Finland’s religious and secular power structures.

“This is the heart of medieval Finland, both ecclesiastically and politically, yet it remains barely explored,” said Georg Haggrén, professor of archaeology at the University of Turku. Early findings include fragments of pottery and glass, which, while unremarkable in isolation, help build a broader picture of daily life. “Every object tells part of the story,” Haggrén added. “Even mundane items—ceramic shards, coins, discarded tools—piece together the bigger narrative.”

Field director Tanja Ratilainen emphasised the value of seemingly minor discoveries, such as refuse pits, which reveal dietary habits and activities through scientific analysis. “What might look insignificant can tell us about trade, craftsmanship, or even social hierarchy,” she said.

The dig also serves as a training ground for students and volunteers, organised by the University of Turku’s archaeology department and the Svenska folkskolans vänner association. Janne Harjula, a university lecturer, noted that modern excavation permits now require detailed plans for post-fieldwork analysis—a contrast to early 20th-century digs led by state archaeologist Juhani Rinne, whose meticulous but undocumented work at Koroinen was only fully published over a century later, thanks to funding from the Kone Foundation.

“Today, we must secure resources not just for digging but for conservation and reporting,” Harjula said. “Rinne was ahead of his time with his notes and sketches, but much early research risks being lost without proper follow-up.”

Koroinen, located 1.5 kilometres from Turku Cathedral, was once a bustling trade hub and the presumed birthplace of the city, traditionally dated to 1229 when the bishopric relocated from Nousiainen. Recent scholarship, however, has challenged this timeline, adding urgency to the current investigations.