Lake Neuchâtel
The Rhône forms a clear boundary between the tectonically-formed Alps and the largely volcanically-formed Massif Central. Moving upstream, the Rhône turns to the east near Lyon, and passes to the south of the Jura range before reaching Lake Geneva. An area of flat ground reaches from there to Lake Neuchâtel, continuing the border, with the Jura to the north-west and the Alps to the south east. From Lake Neuchâtel to its confluence with the Rhine, the Aare forms the border.