It goes through tunnels on a trail next to the lake. After a short climb, it goes downhill and with a bombastic view of the lake! It is worth making the driveway to the lake!
You can reach Switzerland's second-highest dam, the Barrage de Mauvoisin, by road bike. Or at least almost. The last few meters lead through a dark, wet tunnel, which isn't so easy to ride after the approximately 25-kilometer climb.