Between 1901 and 1903 the Commune of Sion built the Sion bisse to take water from the Lienne to the Sionne. At its start, the Sion bisse passes over the Lourantze mountain stream via a wooden aqueduct. It then goes along by Tzeuzier Lake and leaves the Rawyl cirque by a succession of tunnels. Cut into the rock, the canal overhangs a 200-metre drop. Its course then, finally, becomes more peaceful.
Between Tzeuzier and Les Rousses, you can take the itinerary through the tunnels, or you can opt for the old bisse-caretaker path. Warning: this itinerary has a section with ladder and narrow path with handrail to protect from sheer drop. From Les Rousses, you follow the trail by the open bisse to Trédouchet, where you find yourself on the small trail built on the underground bisse. The bisse is again open above the resort. You can also take this circuit in the opposite direction, from the Anzère resort to the dam.
- Difficulty : average
- Duration : roughly 3 hours
- Distance : 10,5 km
- Water-filled : 15 July to 15 September.