Pielisjoki

Pielisjoki is a 67-kilometre long river in Eastern Finland. It is the sixth most fast-flowing river in Finland and the largest river draining into Lake Saimaa. The river connects the two largest lakes in North Karelia, Pielinen and Pyhäselkä. The city of Joensuu is situated at the mouth of the river.

The river was formed shortly after the last glaciation when the Uimaharju esker was broken under the pressure of Pielinen waters, which previously drained north but were redirected by tilting of the ground as a result of post-glacial land uplift.

Source: Wikipedia