Enjoy panoramic city and vineyard views from Festung Marienberg (schloesser.bayern.de; adult/child €4/free), whose construction was initiated around 1200 by the local prince-bishops who governed here until 1719.
Archaeological finds suggest that there was a much smaller fortress here from the 8th century. The construction of what you see today took place over more than five centuries. And the fortress is as impregnable as it looks – its defenses were only breached once, by Swedish troops during the Thirty Years' War, in 1631.
Dramatically illuminated at night, the structure appears to float above the darkness, almost in mid-air like an apparition. Inside, the Fürstenbaumuseum (closed November to mid-March) sheds light on its former residents' opulent lifestyle, while the Mainfränkisches Museum presents city history and works by local late-Gothic master carver Tilman Riemenschneider and other famous artists.
The fortress is a pleasant 25-minute walk uphill through the vineyards from the Alte Mainbrücke via the Tellsteige trail.
