which were built of natural stone. St. Mary's is the epitome of ecclesiastical Brick Gothic architecture and set the standard for many churches in the Baltic region, such as the St. Nicholas Church in Stralsund and St. Nicholas in Wismar. No one had ever before built a brick church this high and with a vaulted ceiling. The lateral thrust exerted by the vault is met by buttresses, making the enormous height possible. The motive for the Lübeck town council to embark on such an ambitious undertaking was the acrimonious relationship with the Bishopric of Lübeck. The church was built close to the Lübeck Town Hall and the market, and it dwarfed the nearby Romanesque Lübeck Cathedral, the church of the bishop established by Henry the Lion. It was meant as a symbol of the desire for freedom on the part of the Hanseatic traders and the secular authorities of the city, which had been granted the status of a free imperial city (), making the city directly subordinate to the emperor, in 1226. It was also intended to underscore the pre-eminence of the city in relation to the other cities of the Hanseatic League, which was being formed at about the same time (1356). The Chapel of Indulgences () was added to the east of the south tower in 1310. It was both a vestibule and a chapel and, with its portal, was the church's second main entrance from the market. Probably originally dedicated to Saint Anne, the chapel received its current name during the Reformation, when paid scribes moved in. The chapel, which is long, deep, and high, has a stellar vault ceiling and is considered a masterpiece of High Gothic architecture. It has often been compared to English Gothic Cathedral Architecture and the chapter house of Malbork Castle. Today the Chapel of Indulgences serves the community as a church during winter, with services from January to March. In 1289 the town council built its own chapel, known as the (Burgomasters' Chapel), at the southeast corner of the ambulatory, the join being visible from the outside where there is a change from glazed to unglazed brick. It was in this chapel, from the large pew that still survives, that the newly elected council used to be installed. On the upper floor of the chapel is the treasury, where important documents of the city were kept. This part of the