The Sulferturm secured the ford to the Grasbödele. Its name derives from the "Sulfurt", the ford that led to the Sule, i.e. the saltworks on the Haalplatz. The tower was probably built together with the city wall around 1250. On the first floor there is a room with a barrel vault that served as a prison. Peasants captured after the Peasants' War of 1525 were held here, and in 1532 the Imperial Mayor Erasmus Büchelberger was also held here. In the 16th and 17th centuries the Sulferturm had a two-story half-timbered structure, which burned down in the Great City Fire of 1728. The rectangular window openings on the 2nd and 3rd floors were broken when the burned-out tower was renovated, and on this occasion it also received its characteristic curved tent roof. The front gate, which was probably an addition from the 15th or early 16th century, may also have been demolished on this occasion.