Wik Castle is one of the best preserved medieval castles in Sweden. The first owner was Israel And in the end of 13th century. The current magnificent castle with seven floors was built in the late 15th century. The massive walls and moats made the stronghold impregnable. During the Middle Ages, the castle was one of the sturdiest strongholds in the Mälaren Valley, and Gustav Wasa once besieged Wik Castle for over a year without ever managing to get inside the walls. It was modified to the present French-style appearance in the 17th century.
Wik Castle has been owned by several noble families like Sparre, Bielke, Horn von Liewe, de Geer and von Essen. Today it is owned by the county council of Uppsala and used primarily for the council's own conference activities. It is at present closed to the public.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.