In his Vita Anskarii, Rimbert describes the Christian mission to the port of the Swedes in the 830s. He mentions two churches there, one built on the family estate of the port bailiff, the other built in the seaport itself by Bishop Gautbert. The loca- tions of these churches have long been discussed. Thanks to archaeological research excavations it is now possible to offer a new suggestion regarding the church of Gautbert. It is argued that the hillfort of Birka, Borg, may be the site of this church and the bishop’s fortified precinct. This would make Birka structurally similar to a number of coeval cities on the Continent, where there was a fortified cathedral hill and a market town at its foot. 9th century finds on and around Borg open up for such a possibility.