Baden is a municipality in the Swiss canton of Aargau, on the west bank of the river Limmat, 25 km northwest of Zürich. It is the seat of the district of Baden. Baden is chiefly visited by reason of its hot sulphur springs, which are mentioned by Tacitus (Histories i. cap. 7) and were very fashionable in the 15th and 16th centuries. They are especially efficacious in cases of gouty and rheumatic affections. They lie a little north of the old town at the river. Many Roman remains have been found in and near the gardens of the Kursaal. The town, dominated on the west by the ruined castle of Stein, is very picturesque, with its steep and narrow streets, its old wooden bridge and its one surviving gateway.
In the 19th and 20th century Baden became an industrial town, main seat of the former Brown Boveri Company. Most industrial faculties have moved, but Baden is still the seat of many of the engineering services of ABB and the power station engineering of Alstom. The big industrial quarter in the north of the city is now being redeveloped into offices, shopping and pleasure facilities.