A Viking Age shipyard at Kugghamn, Birka.

This is a report of an archaeological investigation of maritime remains close to and connected to the Viking Age town of Birka on Björkö, Uppland, Sweden. The investigations included surveys using GNSS receivers and drones, geochemical mapping, and the excavation of four trenches, carried out in August 2020 and August 2021. The investigations were carried out by the Archaeological Research Laboratory (AFL), Department of Archaeology and Classical Studies, Stockholm University. The results show that there was an extensive maritime cultural landscape on the northern part of Björkö, which is rich in remains of different character. One of these remains was investigated in detail by the excavation of four trenches. The feature consists of a dug-out hollow, lined with stones at sides and bottom. Evidence of a wooden contraction was found in the bottom of the hollow in the form of small post-holes, and a stone-frame at the mouth of the hollow towards the waterfront. This is interpreted as the remains of a boat slipway. Rivets, both used and unused, tools for carpentry, and slate whetstones, dominate among the finds and mirror the activities of the site. All is interpreted as evidence for a boat repair site with an associated boat slipway. Finds of e.g. glass beads contemporary with the town Birka, provides a general dating of the remains, possibly with an emphasis towards its later phases of the town. This maritime construction is a unique find with few parallels, but fits well with the other maritime remains in the area. In order to understand its function and dating, it is vital to continue investigations in this important area of Björkö.