The aim of the excavation of Birka’s Black Earth Harbour in 2015/16 was to know more about the wooden extension of the stone-box construction (Swed. stenkista) that formed the jetty, that was archaeologically investigated in 1970/71 (Ambrosiani 1973a; 1973b). This structure is one of the archaeologically best-known harbour facilities on Björkö, although our knowledge so far has, in fact, been confined to its foundations on land. Moreover, the detailed study of the development of the harbour in Birka’s counterpart, Hedeby (Kalmring 2010a), raised questions about both the suggested dating and the dimensions of the facility on Björkö in view of the fact that the technical requirements for trading vessels travelling between Birka and Hedeby had to be met by both harbours.
The two excavation seasons in 2015/16 also satisfied the demand raised by the outcome of the excavation in 1970/71, namely to examine the area in front of the jetty (Ambrosiani 1973a: 13). Furthermore, by selecting the area of an earlier but never fully excavated part of a former trench, intrusion in the UNESCO world heritage site was very limited (fig. 2). A secondary aim was to prolong the 1969 trial trench, which had been dug through most of the silted-up harbour basin, but did not reach as far as the present shoreline. It was thus hoped to connect the information obtained in recent underwater archaeological surveys with the old data from the 1969 trial trench and, with the information from the 1970/71 Black Earth Harbour excavation. It was consequently expected to build up as complete a picture as possible of the harbour activities on Björkö, based on the currently available data.