St. Nicholas Cathedral is a Gothic church established in circa 1247. When the burghers of Elbing (Elbląg) first attempted to adopt the Protestant Reformation in 1525, the provost of St. Nicholas Church maintained Catholic practice. Since 1539 the city council tacitly tolerated and gradually openly promoted Lutheranism, so that St. Nicholas Church had become a Lutheran church by 1573.
Following King Sigismund III's Prussian regency contract (1605) with Joachim Frederick of Brandenburg and his Prussian enfeoffment contract (Treaty of Warsaw, 1611) with John Sigismund of Brandenburg these two rulers of Ducal Prussia guaranteed free practice of Catholic religion in prevailingly Lutheran Prussia. Based on these contracts Prince-Bishop Szymon Rudnicki of Ermland/Warmia achieved the restitution of St. Nicholas as Roman Catholic parish church in 1612, then the only one in Elbing, and remaining a Catholic church since.
St. Nicholas was damaged by fire in the late 18th century, then destroyed in World War II and reconstructed. In 1992, the building was elevated to the status of cathedral.References:
The Petersberg Citadel is one of the largest extant early-modern citadels in Europe and covers the whole north-western part of the Erfurt city centre. It was built after 1665 on Petersberg hill and was in military use until 1963. It dates from a time when Erfurt was ruled by the Electors of Mainz and is a unique example of the European style of fortress construction. Beneath the citadel is an underground maze of passageways that can be visited on guided tours organised by Erfurt Tourist Office.
The citadel was originally built on the site of a medieval Benedictine Monastery and the earliest parts of the complex date from the 12th century. Erfurt has also been ruled by Sweden, Prussia, Napoleon, the German Empire, the Nazis, and post-World War II Soviet occupying forces, and it was part of the German Democratic Republic (East Germany). All of these regimes used Petersberg Citadel and had an influence on its development. The baroque fortress was in military use until 1963. Since German reunification in 1990, the citadel has undergone significant restoration and it is now open to the public as a historic site.