Although virtually all city sights are within a half-mile radius, the Marienberg Fortress is a substantial climb. Those with limited endurance or time may wish to go by car (city buses also stop at the castle entrance), since the imposing structure is built high on a bluff overlooking the Main and the city. Those who prefer to walk can pass the 13th-century Romanesque Town Hall and cross the river via the Alte Mainbrücke, built in the 15th and 16th centuries and lined with a dozen deeply emotive statues of saints added during Baroque times.

Other than the Marienberg itself, the bridge offers perhaps the best views in Würzburg, to the Altstadt, to the vineyards and to the fortress itself. Across the river, two walking routes lead to the castle, one directly and steeply up a series of stairs and paths, the other along a more gradual trail that winds through the vineyards that surround nearly three sides of the castle. The latter route may take twice as long as the first (about 50 minutes at a good pace), but it's more scenic - and easier on the knees and thighs.

Like the rings of a giant redwood, the oldest part of the castle is in the center, the 8th-century Marienkirche. When it became the home to the prince-bishops in the early 13th century, the foundation of the fortress itself was built, followed by the trademark medieval ring wall - with moat and drawbridge - in the late 15th century.

Around 1600, the Renaissance "princely apartments" were added, which still stretch grandly above the stone walls. During the same period, a well was constructed stretching more than 300 feet to the level of the Main as an emergency drinking source. A look into it is dizzying. Later in the century, the prince-bishops extended the castle in Baroque style with the commandant's apartments and castle arsenal.

The view from the fortress offers a good first stop to get one's bearings. To the east, across the Main, the Altstadt is bordered by a series of streets that (with a little imagination) form the shape of a bishop's hat. To the north, the vineyards of the Steinberg climb terrace upon terrace up a craggy, rolling hillside. (Indeed, vineyards on the Marienberg are so close to the city that vines would threaten traffic if not otherwise tamed.)

The skyline is dominated by churches representing nearly a millennium of architectural styles: St. Kilian's, Neumünster, St. Mary's Chapel, St. Peter's, St. Stephan's, St. Gertraud's, Augustinerkirche, St. Johannis', Karmelitenkirche, and - on a wooded hill to the south - the pilgrimage church Käppele, significant not just for its impressive frescoes but for the stations of the cross - with life-size sculptures - along the pilgrimage path.

Marked routes make walking easy and match up with a free Visitor's Guide and map available at the City Tourist Office and other locations. The tour (about two hours, excluding time spent visiting buildings) passes most major sights and provides a good orientation and starting point for more individualized exploration. Watch out for streetcars, which seem to come out of nowhere.