For over 700 years Örebro Castle has kept a watchful eye on everyone crossing the bridge on the River Svartån. The oldest part of the castle, a defence tower, was erected in the latter half of the 13th century. This tower was added to in the 14th century to make a larger stronghold. The castle was expanded during the reign of the royal family Vasa between 1573-1627 to the impressive Renaissance castle.
After Vasa family Örebro castle was left to decay, but the main restoration took place in 1758-1764 by Carl Johan Crondstedt. After him the castle was used as a residence of county governor. The castle was finally restored to the 16th century appearance between 1897-1900.
Today there are guided tours, an exhibition centre and the castle is a very worthwhile sightseeing destination.
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.