This important monument of the Trier archbishops forms one of the few remaining medieval city castles in the Upper Middle Rhine Valley. Construction of the keep began as early as the second half of the 13th century. The estate on the left bank of the Rhine is also called "Balduinsburg" after the builder of its west wing, Balduin of Luxembourg. In 1327, Balduin had to recapture "his" town and castle from rebellious citizens. In the Middle Ages, the impressive city castle with its castle character served as an imperial castle and an electoral customs office. Elector Johann II of Baden, the founder of the University of Trier, once resided here. The Boppard Museum, which has been located in the castle for over 100 years, presents excerpts from the town's history. The extensive collection of bentwood furniture tells the story of Michael Thonet, a son of the town of Boppard, who started as a craftsman with an idea and created a world enterprise. In addition, regularly changing exhibitions of contemporary art and events are part of the museum's programme.