The original castle on the Marienberg, a hill which was first settled in the late Bronze Age, was probably a small fort built early in the 8th century by the Franconian-Thuringian dukes. The circular Marienkapelle is one of the oldest church buildings in South Germany and dates from around 1000. From 1200 an unusually large castle was built, which was extended during the late Middle Ages and the Renaissance. For half a millennium, from around 1250 to 1720, the Marienberg was the ruling seat of the Würzburg prince-bishops, who also held the title of Duke of East Franconia.

Following the storming of the castle by the Swedes in 1631, Prince-Bishop Johann Philipp von Schönborn built a circle of massive bastions, which are the dominant feature of Marienberg Fortress. In 1945 the fortress was almost completely burned out, and its reconstruction was only completed in 1990.

St Mary’s Church (Marienkirche), which dates back to AD 706, the forty-metre-high keep and the well house with a cistern over 100 metres deep are impressive monuments to an over 1000-year history.

The 1,300 square-metre Princes' Garden is accessible from the castle courtyard: it was reconstructed in on the basis of plans dating from the early 18th century.