The castle Stein was formerly a stronghold of the Habsburgs, but destroyed in 1415 and again in 1712. In 1415 Baden (with the Aargau) was conquered by the Eight Swiss Confederates, whose bailiff inhabited the other castle, on the right bank of the Limmat, which defends the ancient bridge across the river. As the conquest of the Aargau was the first made by the Confederates, their delegates (or the federal diet) naturally met at Baden, from 1426 to about 1712, to settle matters relating to these subject lands, so that during that period Baden was really the capital of Switzerland. The diet sat in the beautifully carved diet hall in the town-hall or Rathaus, which can be visited. There was also signed in 1714 the Treaty of Baden which put an end to the war between France and the Holy Roman Empire, and thus completed the treaty of Utrecht (1713). Baden was the capital of the canton of Baden, from 1798 to 1803, when the canton of Aargau was created.
In the 19th and 20th century Baden became an industry town, main seat of the former Brown Boveri Company. Most industrial faculties have moved, but Baden is still the seat of much engineering services of ABB and the power station engineering of Alstom. The big industrial quarter in the north of the city is now changing to offices, shopping and pleasure facilities. In 2002 the permanent population of Baden was 16,000.
One mile S. of Baden, on the Limmat, is the famous Cistercian monastery of Wettingen (1227-1841), with splendid old painted glass in the cloisters and magnificent early 17th century carved stalls in the choir of the church. Six miles W. of Baden is the small town of Brugg (9500 inhabitants) in a fine position on the Aare, and close to the remains of the Roman colony of Vindonissa (Windisch), as well as to the monastery (founded 1310) of Koenigsfelden, formerly the burial-place of the early Habsburgs (the castle of Habsburg is but a short way off), still retaining much fine medieval painted glass.