The Kalanti stone church, today part of Uusikaupunki city, was built between years 1430 and 1450. The interior is covered with famous wall paintings signed by Petrus Henriksson in 1470s. The oldest altarpiece in Finland was originally in the church of Kalanti. It was made by German master Francke in the beginning of 15th century and stood in Kalanti church until 1883. According the local legend, collected in the 19th century, the altarpiece was found floating in the sea outside Kalanti. The altarpiece is now located at the National Museum of Finland.
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.