Topographic map of the Kymi river. The dashed line indicates the passage of the river inside lakes, not as a river stream per se. In the inset map, the lighter area indicates the drainage basin of the Kymi river.
Own work

Topography: Elevation model 2 m / National Land Survey of Finland (open data, CC BY 4.0)
Labels: Geographic names / National Land Survey of Finland (open data, CC BY 4.0)
Drainage basins: Valuma-aluejako / Finnish Environment Institute SYKE (Attribution 4.0 International (CC BY 4.0))
Shoreline, Lakes, Cities: Topographic map 1:250 000 / National Land Survey of Finland (open data, CC BY 4.0)
Rivers: Ranta10 - rantaviiva 1:10 000 / Finnish Environment Institute SYKE (Attribution 4.0 International (CC BY 4.0))
Inset map: 1:10m Cultural – Admin 0 – Countries / Natural Earth
Nelg