Château de Rouen was a castle built by Philip II of France from 1204 to 1210 following his capture of the duchy from John, duke of Normandy and king of England. Located outside the medieval town to its north, in a dominant position, it played a military role in the Hundred Years' War and the Wars of Religion. It was the main seat of power, administration and politics in the duchy of Normandy for nearly 400 years.
It was here that Joan of Arc was imprisoned in December 1430 and tried from 21 February to 23 May 1431. Vulnerable to artillery like other medieval fortresses, all but the keep (now known as the Tour Jeanne d'Arc) was dismantled in 1591 by Henry IV of France. The pointed roof of the keep was added in restoration works beginning in the 1870s. During the Second World War the tower was camouflaged and turned into a bunker by the occupying German forces. It is now open 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.