Fortress Marienberg is a prominent landmark on the Main river in Würzburg, Germany. The mighty Fortress Marienberg is the symbol of Würzburg and served as a home of the prince-bishops for nearly five centuries. It has been a fort since ancient times. After Gustavus Adolphus of Sweden conquered the area in 1631, the castle was reconstructed in the Baroque style. Today, it is a park and museum.
A refuge castle was at this site from at least the late Bronze Age (Urnfield culture). The oldest extant structure is Saint Mary's Church (Marienkirche), built in AD 704. The fortifications date to the 13th century. The castle became the residence of the prince-bishops of Würzburg in 1253.