oldest parts of the current building probably belong to the church which was inaugurated in 1306. During the entire Middle Ages, the main patron saint of the church was Saint Nicholas. Several churches in the Baltic region from the 13th century are dedicated to Saint Nicholas, especially in cities where the Hanseatic League had a presence, as was the case in Stockholm. The church was also dedicated to Saint Mary and Saint Eric. The church remained the only parish church of Stockholm, serving the entire city, until the 1590s. In general, the medieval history of the church building is complex and difficult to determine in detail. There are few written sources, and a lack of ornaments has made it difficult to draw any conclusions about the age of the different parts on stylistic grounds. Originally, the church appears to have consisted of a nave with two aisles. It had a wooden ceiling supported by six pillars. The building material was brick. The main entrance was probably located to the west, though side entrances may have existed in the north and south walls. Stylistically, the church was part of a group of brick churches built in the area around Lake Mälaren at the time, including Strängnäs Cathedral, St. Mary's Church, Sigtuna and . The church was successively rebuilt and enlarged during the 14th and 15th centuries. Embellishing the church was a way for both the monarchs of Sweden and the citizens of Stockholm to demonstrate their power and influence. A donation to the church in 1346 by King Magnus IV and his wife Blanche of Namur probably indicates that the first of a number of chapels had been added to the church. This chapel was originally dedicated to Saint Mary and was located at the south side of the east end of the church. The four bays that belonged to the chapel are still discernible in the interior of Storkyrkan. Similar chapels were built at approximately the same time at Visby Cathedral and St. Mary's Church, Lübeck. The chapel was decorated with Early Gothic murals in a style unusual for Swedish churches (later heavily restored). A second chapel was added to the church sometime before 1361, and further chapels were built during the early 15th century. By the end of the Middle Ages, Storkyrkan contained more than 30 chapels or specifically dedicated altarpieces, an amount only comparable with the cathedrals of