Mersch Castle is one of the castles belonging to the so-called Valley of the Seven Castles. The castle was built in the 13th century by Theodoric, a knight in the service of Countess Ermesinde of Luxembourg. It was captured and burnt down by the Burgundians. In 1574, Paul von der Veltz transformed the building into a comfortable castle in the Renaissance style. The keep had large windows and the property was surrounded by a protective wall with seven towers. Finely vaulted ceilings were erected over the rooms on the ground floor and the first floor. The Knights' Hall on the second floor has a magnificent chimney. The arms of 16 noblemen decorated the walls. In 1603, the castle was again destroyed by the Dutch. In 1635, during the Thirty Years' War, the castle and the village were left in a sorry state. However, around 1700, it was once again repaired, this time by Johann-Friedrich von Elter who rebuilt the gate and appended his coat of arms. The chapel was restored in 1717 by von Elter. The altar bears the arms of the castle's heiress, Charlotte von Elter.
In 1898, the Sonnenberg-Reinach family sold the castle to a businessman called Schwartz-Hallinger. In 1930, restoration work was carried out by the owner M. Uhres. In 1938, a youth hostel was housed in a new building adjacent to the castle. From 1957, the commune acquired the building but sold it to the State of Luxembourg in 1960. As a result of an exchange agreement, the commune finally regained ownership in 1988 and undertook substantial renovation work for the needs of itse administrative services which now occupy the building.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.