The city was founded in 1844 when Michael Drewsen started a paper mill at the spot next to the river. The city is divided north and south by the lake Silkeborg Langsø, which at the eastern side of the city, resolves into the Gudenå River. The area is known as Søhøjlandet, the lake highland, and Silkeborg is located in a very hilly landscape surrounded by Denmark’s largest forest district and a great number of lakes. One of these lakes, Slåensø, is considered to be among the cleanest in Denmark