It was quite a rainy weekend here in Switzerland. The best chance was in the west. So I took the train heading west. And I ended up in Lac de Joux. That's the biggest lake in the Jura mountains. It's feeded by the Orbe and it doens't really has an outlet. Most of the water seeps through the ground and exits in Vallorabe.
I started in Le Pont, and went around the lake. That's about 23 km.