Wulp Castle was built during the high Middle Ages. Despite this, the castle is documented only in a few found texts, and much of the castle's history is not known. However, in the chronicle of Muri Abbey, a castle that could perhaps fit Ruine Wulp's description - a castle in proximity to Zurich and Lake Zurich - was mentioned, but this has not been confirmed by other findings and is mere speculation. Also, a person named Eghart of Küsnacht was mentioned in the chronicle and several other documents to be the owner of the castle in the late 11th century. The castle was probably destroyed or abandoned already in the 13th century.
While no cemented and sure truth about the castle can be confirmed, progress has been made, including the finding of Bronze Age remnants after the excavation of the castle site, such as palisades. Other items have been uncovered about the castle's past, such as the altering of the castle in the 13th century, when it is presumed that most or all of the castle was replaced with a single tower and a central building, with only sections of the main wall still existing. After an unknown period of time, the Barons von Regensbergare known to have assumed ownership of Ruine Wulp, and also are known to have made plans to completely renovate the castle, but the plans probably were never realised.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.