Birka, on the island of Björkö in Lake Mälaren, 40 kilometres from Stockholm, is thought to be Sweden's oldest town and has been the site of excavations since the 17th century.
But there is still plenty left to be discovered on the island, as Swedish and German researchers' latest find proves.
Thanks to high-resolution geophysical surveys carried out in September 2016, researchers now believe they have located one of the most important Viking halls of the era, situated in the harbour bay of Korshamn, outside of Birka's town boundaries. They believe that it can be dated to the period after 810 AD.
“This kind of Viking period high status manors has previously only been identified at a few places in southern Scandinavia, for instance at Tissø and Lejre in Denmark,” said Johan Runer, archaeologist at the Stockholm county museum, in a statement.
The hall is around 40 metres long and its size suggests it could only have belonged to the most senior person on the island, the King's representative and Birka's royal bailiff Herigar.
Established in the middle of the 8th century, Birka was the Baltic link in the river and portage route to the Byzantine Empire. Birka was also important as the site of the first known Christian congregation in Sweden, founded in 831 by Saint Ansgar. It has been a Unesco World Heritage Site since 1993.
Herigar is said to have built the first Christian church in Sweden on the island, and researchers have found a large fenced area connected to the hall, which may have been used for religious activities.
“The site could say something very important about the establishment of the town of Birka, because it is a place that dates back further than Birka,” added Runer in an interview with the TT newswire.
Another manor predating the establishment of the Viking Age town has also been found on the site.
“The consequences of our discoveries cannot be overestimated: in terms of the emergence of the Viking town of Birka, its royal administration and the earliest Christian mission to Scandinavia,” said Sven Kalmring of the Zentrum für Baltische und Skandinavische archäologie in Schleswig.
The discoveries are the result of a collaboration between Zentrum für Baltische und Skandinavische Archäologie, Stockholm county museum and Stockholm's University's Archaeological Research Laboratory.