Akerselva (the Aker River) in Oslo divides the city.
The river divides the city and it’s about 8.2 kilometres long, and has a difference in altitude of approximately 149 meters.
The Old Norse name of the river was Frysja, and this old name has been revived as the name of a neighborhood along the river. The name is probably derived from the verb frusa ‘froth’, referring to the many waterfalls in the river. The river is mentioned several times in Sverris saga
Check Wikipedia for more info on Sverris saga: http://en.wikipedia.org/wiki/Sverris_saga