A question when you refer to the map the red lines are the river systems, that is what this word means .---> Salpausselkä Ridge
A question when you refer to the map the red lines are the river systems, that is what this word means .---> Salpausselkä Ridge
The red lines are not rivers. They are ridges. Salpausselkä is a name.
See the Cambridge Dictionary definition of ridge.