The Château d'Étampes was a castle in the town of Étampes. The principal remains are of the 12th-century keep, the Tour de Guinette.
The Château d'Étampes was an early 10th-century stronghold of Robert the Pious, King of France, that comprised both a palace proper and motte. Between 1130 and 1150, a new castle was created overlooking the valley, culminating in a strong keep or donjon: the present Tour de Guinette. The Château was extended under later kings, notably Philip II of France, but suffered through sieges in the Hundred Years War before having been ordered destroyed by Henry IV of France, after which only the keep remained.
The architectural aspects of this former royal castle are known from contemporary images, including the Très Riches Heures du duc de Berry. Tour de Guinette was in the center of the castle and was surrounded by a rectangular curtain wall punctuated by corner towers. This wall was, in turn, enclosed by two additional walls providing layers of defense for the keep.
The surviving keep stands roughly 27 meters tall and is a quatrefoil plan (much like a four-leaf clover). Divided into four stories, first-floor access may originally have been reached from the enclosure wall. This interesting plan is the result of tactical experimentation that the keep underwent during the mid-12th century to improve the defense of towers against missiles and to reduce dead ground. The circular lobes deflect missiles, and allow defenders to cover the foot of the walls from the summit of the keep. The plan resembles the keeps of Ambleny and nearby Houdan. Clifford's Tower, part of York Castle in York, England, is believed to have been inspired by Étampes.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.