The remains of the Castle can be visited
Mosburg Castle (Ruin) (Wiesbaden-Biebrich)

The Mosburg ruin in Wiesbaden-Biebrich was built on the remains of the royal palace Biburc. Originally conceived as an artificial ruin in Biebrich Palace Park, it now embodies a blend of historical depth and aesthetics.
History+
The origins of the Mosburg date back to a royal palace called Biburc, which existed in the 11th century and was initiated by Louis the German. In the 13th century, a moated castle is said to have stood on this site. A comital Nassau manor house is mentioned in 1462. From 1654, ownership passed to the Swedish envoy Penz von Penzau. In the early 19th century, Duke Friedrich August of Nassau acquired the remains of the buildings. He commissioned Carl Florian Goetz to construct a neo-Gothic residential castle on the old foundations, which was completed between 1805 and 1806. Materials from Mainz's Liebfrauenkirche were used for the construction. This mock ruin served the Nassau dukes as a retreat and temporarily housed epitaphs from Eberbach Monastery.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 50.0460, 8.2371