The Aarau River is a river located in the Canton of Aargau in Switzerland. It flows for approximately 35 kilometers, starting from the Reuss River near Aarau and eventually joining the Aare River. The river is known for its picturesque landscapes and is a popular spot for outdoor activities such as hiking and fishing. The Aarau River plays an important role in the local ecosystem, providing habitat for various species of fish and wildlife. Its waters are also used for irrigation and recreational purposes. The river's banks are lined with walking paths, making it accessible for both residents and visitors to enjoy its natural beauty.