A former Benedictine monastery on the south bank of the Lech river, founded in the 9th century around the grave of the missionary St. Magnus and rebuilt in High Baroque style between 1701 and 1717 by Vorarlberg architect Johann Jakob Herkomer. The church interior is a stuccoed, gilded, and frescoed festival of pinks, golds, and pale greens — characteristic Bavarian baroque at its lightest.
The conventual buildings now house Füssen town hall and the Stadtmuseum (city museum), with exhibits on the town's history as a centre of lute and violin making — Füssen luthiers supplied the courts of Europe in the 16th and 17th centuries. The Romanesque crypt below the church preserves the oldest surviving wall paintings in Bavaria. Free entry to the church; small fee for the museum. Closed Mondays.