Baden (German for "Baths"),sometimes unofficially, to distinguish it from other Badens, called Baden bei Zürich ("Baden near Zürich") or Baden im Aargau ("Baden in Aargau"), is a municipality in Switzerland. It is the seat of the district of Baden in the canton of Aargau. Located 25 km (16 mi) northwest of Zürich in the Limmat Valley (Limmattal) mainly on the western side of the Limmat, its mineral hot springs have been famed since at least the Roman era. Its official language is (the Swiss variety of Standard) German, but the main spoken language is the local Alemannic Swiss German dialect. Its population in 2010 was over 18,000.