The Begna runs from the mountainous area of Filefjell in the southern part of the Jotunheimen range, through the traditional district of Valdres into the lakes Vangsmjøsi, Slidrefjord, Strondafjorden and Aurdalsfjorden, down Begnadalen to Nes in Ådal and Lake Sperillen via the Ådal River and southward to the city of Hønefoss in Viken.