Aarau is a town, a municipality, and the capital of the northern Swiss canton of Aargau. The town is also the capital of the district of Aarau. It is German-speaking and predominantly Protestant. Aarau is situated on the Swiss plateau, in the valley of the Aare, on the river's right bank, and at the southern foot of the Jura Mountains, and is west of Zürich, 58 kilometres (36 mi) south of Basel and 65 kilometres (40 mi) northeast of Bern. The municipality borders directly on the canton of Solothurn to the west. It is the largest town in Aargau. At the beginning of 2010 Rohr became a district of Aarau.

The 26 cantons of Switzerland are the member states of the Swiss Confederation. The nucleus of the Swiss Confederacy in the form of the first three confederate allies used to be referred to as the Waldstätte. Two important periods in the development of the Old Swiss Confederacy are summarized by the terms Acht Orte and Dreizehn Orte.