Westerturm, Gate tower in Duderstadt, Germany.

The Westerturm is a gate tower of Duderstadt's medieval city wall, marked by its distinctive twisted roof. The structure sits at the western entrance to the old town and stands amid lanes that lead toward the two main churches.

A predecessor gate, recorded as "valva inferior" in 1343, burned down with much of Duderstadt on 17 April 1424. Construction of the present tower began on 14 June of that year, and the rebuild was completed in 1506 with the placing of the tower finial. A structural analysis in 1999 found the tower at risk of collapse, leading to restoration from 2002 to 2004.

A local legend blames the devil for the twisted spire: a builder in a hurry made a pact with him, then broke it, and the devil seized the roof tip and swung around it, bending the rafters. The tower now houses a museum of the town's history, and with the Bachmann'sches Haus and the Schützenmuseum it forms a museum ensemble at the north-western entrance to the pedestrian zone.

The tower is partly open to the public and houses a museum of town history; it forms a museum ensemble with the Bachmann'sches Haus and the Schützenmuseum at the northwestern entrance to the pedestrian zone. The tower was closed for extensive restoration from 2002 to 2004 and reopened on 12 August 2004.

The twisted spire stems from a construction flaw in the roof truss, not from a weather vane. A local legend instead blames the devil: a builder in time trouble signed a contract with him, then refused to pay with his soul, so the devil seized the spire and swung around it, bending the rafters.