Ansgar arrived at Birke near Stockholm in AD 829 and converted the royal bailiff. New surveys indicate his first church may have been found.
In AD 829 the Benedictine monk, Ansgar, travelled to Birka (Björkö) on Lake Mälaren in a response to a request from the Swedish king, Björn of Hauge. It took Ansgar twenty days to get there, but when he arrived, the king received them in a friendly manner and allowed the Christian missionaries to set up shop. According to the Vita of Ansgar written by Rimbert c. 875, they had some success as the local chieftain or bailiff, Herigar, allowed himself to be baptized. “Not long after, he built a church on his private land” (hereditas), we are told.
Since archaeologists began excavating at Birka in the 17th century, one of the holy grails have been to find the exact location for this – arguably – first church built in Scandinavia. Later excavation in the 19th and 20th century have found multiple artifacts that witness to the existence of a probable Christian congregation – pendants in the form of crosses and crucifixes as well as a Frisian jug decorated with applied tin foil in the form of crosses. This piece of Tattinger ware might have been used as a baptismal jug. Until now, though, the identification of Herigar’s manor – and church – has eluded the archaeologists.
Recently, however, high-resolution geophysical surveys using ground-penetrating radar have been carried out near Korshamn, one of the major harbours on the island of Björkö, situated outside the town boundaries of the Viking town of Birka.
Until now the role of Korshamn has represented an enigma, located as it was outside the boundaries of the town and with the main burial ground, Hemlanden, stretching out in between. This is curious in so-far as the waters at Korshamn are much calmer. Archaeologists have long speculated why the town was not built near this natural inlet. We now know that the harbour and the land around in all likelihood was the private property of Herigar; and the town was shifted aside.
The reason is that he survey revealed a major Viking period hall on site, with a length of around 40 meters. Based on the land upheaval, the area surrounding the Viking hall can be dated to sometime after 810 AD. The hall was connected to a large fenced area that stretches towards the harbour basin.
“This kind of Viking period high status manors has previously only been identified at a few places in southern Scandinavia. It is known that the fenced area at such manors was linked to religious activities” says Johan Runer, archaeologist at the Stockholm county museum.
The survey has revealed that the hall at Korshamn would have measured app. 37 x 11.5. This equals the halls at Tissø, Erritsø (both Denmark) and Järrestad, which were all fitted with near-by in-fenced buildings like the one, which was been located at Korshamn. Such in-fenced buildings have invariably been identified as probable cult-buildings measuring app. 20 x 6 m. So-far, the size of the in-fenced building at Korshamn has not been determined.
During the survey a predecessor for the Viking Age manor was also identified at the site: a high status manor that existed during the Vendel period, prior to the establishment of the Viking Age town of Birka. Both the identified buildings and their continued use from the Vendel period to the Viking Age correlate well with the “ancestral property” of Birka’s royal bailiff Herigar as mentioned in Rimbert’s Vita Anskarii.
This is also indicated by the place-names. Next to Korshamn lies a small inlet, called Salviken, which has hitherto been identified as salu-viken (sale-bay) or salt-viken (salt-bay). In view of the new finds, it is, however, more reasonable to understand the place-name as meaning salr-viken, the bay with the ‘Salr’ aka the ‘hall’. This may be supplemented with the fact that Kalhagen was identified in a folklore source from 1896, “as the place where the temple stood” . Perhaps even more fascinating is the discussion of the place-name ‘Korshamn’, literally Cross-Harbour. According to Norse sources, marks pinpointing the entrance into harbours might in a later period be indicated by a cross. If Korshamn is identical with that of ‘portus sancti Ansgarrii’ mentioned by Adam of Bremen  it may even pay off to look for the grave of another missionary, Unna. He went there in 935 in order to re-establish the Christian mission at Björkö, but died there and was according to Adam buried there, while his head was transported back to Bremen to be interred in the cathedral . The grave in Bremen was in all likelihood identified there in 1973 -76. Whether his bones were laid to rest inside or nearby the former church of Ansgar remains to be seen, if and when excavations are undertaken at Korshamn in the future.
“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”, says Sven Kalmring, researcher at the Zentrum für Baltische und Skandinavische Archäologie, Schleswig.
“The results highlight the benefits of using non-intrusive geophysical surveys for the detection of archaeological features and, once again, prove to be an invaluable tool for documenting Iron Age building remains in Scandinavia”, says Andreas Viberg, researcher at the Archaeological Research Laboratory at Stockholm University.
The results will be published in the international scientific journal Archäologisches Korrespondenzblatt volume 2017/1.
The research has been carried out as part of a collaboration between Zentrum für Baltische und Skandinavische Archäologie, Stockholm County Museum and the Archaeological Research Laboratory, Stockholm University.
 Kalmring 2017, p. 18
 Magistri Adam Bremensis Gesta Hammaburgensis Ecclesiae Pontificum. Hannover and Leipzig, 1917: lib. IV, chapt. 21, schol.127.
 Op. cit. Magistri Adam… lib. I, chapt. 62
At Home with Herigar: A magnate’s residence from the Vendel- to the Viking Period at Korshamn, Birka (Uppland/s)
By S. Kalmring, Johan Runer and Andreas Viberg.
In: Archaeologisches Korrespondenzblatt (2017) no. 1, pp. 1 – 27
Major Viking Age Manor Discovered at Birka, Sweden
January 19, 2017
News provided by the University of Stockholm.
Birka and Hovgaarden.
Swedish National Heritage Board
Reconstruction of Herigar’s manor at Birka. Reconstruction by Jacques Vincent. Provided as part of Press release by Stockholm University