Bischofszell castle was built in the 12th/13th century. It was damaged by the city fire in 1419 and repaired soon thereafter. During the 17th and 18th century the castle was expanded and totally renovated. The newly founded Canton of Thurgau took over the castle in 1798, but sold it in 1811 again. About 1838 the west part collapsed, and in 1843 the keep was broken up. Since 1930, the castle has been owned by the municipality.
The old bridge, constructed in late gothic style, was inaugurated in 1487. It is the oldest bridge in the entire region.
The Château de Foix dominates the town of Foix. An important tourist site, it is known as a centre of the Cathars. Built on an older 7th-century fortification, the castle is known from 987. In 1002, it was mentioned in the will of Roger I, Count of Carcassonne, who bequeathed the fortress to his youngest child, Bernard. In effect, the family ruling over the region were installed here which allowed them to control access to the upper Ariège valley and to keep surveillance from this strategic point over the lower land, protected behind impregnable walls.
In 1034, the castle became capital of the County of Foix and played a decisive role in medieval military history. During the two following centuries, the castle was home to Counts with shining personalities who became the soul of the Occitan resistance during the crusade against the Albigensians.