The powerful Hanseatic city of Stralsund boasted a rich medieval visual art. This is particularly evidenced by the largely preserved church furnishings of St. Nicholas. However, its historical form, as well as that of the other 15 former churches and chapels in the city with their 207 altars, has remained completely unknown for the period before 1525. Previously, there was only an idea of richly decorated altars that fell victim to the Reformation's iconoclasm and thus have not survived. Despite a sparse record regarding the visual art of the altars, the author re-examined the existing material using a method that also considers the preserved works as primary sources. The analysis of the characteristics of the works, combined with a concurrent exploration of local history, thus revealed the true history of the object.