Schlossstraße 1, 56112 Lahnstein
Apart from its function as a toll castle, the Martinsburg Castle, constructed in the first half of the 14th century, served as a citadel and retreat for the Archbishops of Mainz; it was separated from the urban space by a moat.
The complex, which has been extended several times, has remained entirely preserved. The Gothic donjon in the southern corner and the more recent Baroque building from the 18th century joined onto it are true eye catchers. Around 1500, residential buildings were renovated so that large parts of the complex reveal Renaissance elements. Today, the Castle houses a carnival museum in addition to private apartments and offices; in addition, the outer complex and the park can be visited. Scenic tours are offered around the castle and in the inner courtyard.