The Huys Dever is a small castle probably built shortly after 1375 by Reinier Dever or d'Ever, a member of an old noble family from Holland. The castle was a typical stronghold that was at one time situated on the edge of a lake called the Lisser Poel (since poldered in) that itself was in connection to the Haarlemmermeer (itself a polder since in 1853). In 1630 a stately home was built on to the tower and became a summer residence, but after the Haarlem Lake was poldered in the 19th century it fell into disuse and became a ruin. In 1973 restoration began and the roof was built in the manner of 16th century carpentry.
The building houses a small archeological museum with finds dug up in the former moat around the building. It has been voted a very important rijksmonument for its early medieval remains. The building is open to visitors.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.