From the Wikipedia page 
The Stadtarchiv Stralsund is the historical Archive of the Hanseatic City of Stralsund and an important municipal archive in Mecklenburg-Vorpommern, Germany.
The Stadtarchiv Strasund ranks among the important communal archives in Europe, as it covers the cities role in the Hanseatic League and the history of Swedish Pomerania. This municipal archive has been taking custody of records in Stralsund since the Middle Ages.
More information on the German Wikipedia page 
The website is