Alte Thurbrücke, Medieval stone bridge in Bischofszell, Switzerland

The Alte Thurbrücke is a stone arch bridge spanning the Thur River in Bischofszell, built in 1487 with eight arches constructed from sandstone and tuff stone blocks. The structure stretches about 116 meters and curves slightly, following the natural rock formations that serve as the foundation for its supporting pillars.

Built in 1487, this bridge replaced an earlier wooden crossing that had stood upstream since at least 1325. The shift to stone construction represented a major upgrade in the permanence and reliability of river crossings in the region.

The bridge's nickname, Krumme Brücke ("Crooked Bridge"), comes from its bent ground plan: the piers had to sit on the Nagelfluh rock in the riverbed, which does not lie in a straight line. A legend tells that two noble youths drowned in the swollen Thur, which is said to have prompted the 1479 agreement between Bischofszell and Bishop Otto IV of Constance to build a stone bridge over the Thur and the Sitter.

The bridge is located right in the village center and is easily accessible on foot from nearby streets. Extensive restoration work completed between 1999 and 2006 strengthened the structure, making it safe and stable for pedestrian crossing today.

Rather than crossing the river in a straight line, the bridge curves to follow the natural rock formations that support its pillars in the riverbed. This adaptation to the landscape shows how medieval builders worked with what nature offered rather than against it.