Lac de Cleuson Bike Climb | Cycling the Swiss Alps

Switzerland Lac de Cleuson

Lac de Cleuson Bike Climb - PJAMM Cycling

32.1

PDI

15.7 mi

DISTANCE

5,267 ft

GAINED

ELEVATION GAINED

6.4 %

AVG. GRADE

AVG. GRADIENT

FULL CLIMB STATS

Page Contributor(s): Ard Oostra, Montreux, Switzerland

INTRO

Lac de Cleuson climbs 15.7 miles and 5,267 feet from Sion, the largest city in Valais, up the Nendaz valley to a turquoise reservoir tucked beneath the Rosablanche massif at just over 2,100 meters. The average grade is a moderate 6.35%, steady enough to settle into a rhythm rather than survive in bursts. The route climbs straight through the Nendaz ski area - Super-Nendaz sits roughly halfway up - before reaching Siviez, where the pavement ends and a gravel road, including a short tunnel and a run of hairpin bends, carries riders the rest of the way to the dam. The lake itself is known for a striking turquoise color, and a small stone chapel, Saint-Barthelemy, sits on its shore - the highest and oldest chapel in the commune of Nendaz, documented as far back as 1447. Lac de Cleuson is a working part of the Grande Dixence hydroelectric scheme - its water is pumped uphill into Lac des Dix, in the neighboring valley to the east, where the Grande Dixence dam (the tallest gravity dam in the world) is the centerpiece of a separate PJAMM climb starting from this same Sion hub. Between the ski resort, the reservoir, and the dam-building history, this is as much an engineering tour as a bike climb.

PLAN YOUR ROUTE

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Lac de Cleuson gains 5,267 feet over 15.74 miles at a 6.35% average grade, one of the more evenly-paced climbs among Valais's high-value routes. The lower miles through Basse- and Haute-Nendaz warm up gradually before the road settles into a consistent grade through the ski area. The steepest riding comes on the gravel finish above Siviez, where the steepest quarter-mile reaches 11.6% - a real jump from the sustained-but-moderate pitch of the paved miles below. Riders should expect that final push, tunnel and hairpins included, to feel noticeably harder than the average grade suggests.

Roadway: The road is paved from Sion through Nendaz and Haute-Nendaz to the Siviez ski station, then turns to a well-used gravel road for the final stretch to the dam - wide enough for maintenance vehicles, with a short tunnel and a series of hairpin bends before the lake comes into view. Standard road tires handle the gravel section in dry conditions, though wider tires add confidence given the hairpins and the tunnel's uneven surface.

Traffic: Traffic is moderate through the Nendaz resort area, especially in summer when the valley is busy with hikers and mountain bikers, then drops off substantially above Siviez - the gravel finish sees mostly cyclists and hikers rather than regular car traffic.

Parking: Siviez has a dedicated parking area at the base of the gravel section, a natural spot to regroup or start from if you'd rather skip the lower, more built-up miles through the resort. Sion, at the start, has ample parking near its train station.

Sion and the villages of Basse- and Haute-Nendaz have full services - grocery stores, cafes, and bike shops - so there's no need to carry much for the lower two-thirds of the climb. Siviez has some resort-season food options, but plan to be self-sufficient above there, since there's nothing at the lake itself beyond the chapel. Because the final miles are gravel, tire choice matters - riders report that 28mm or wider tires handle the hairpins and the short tunnel more comfortably than a narrow race tire. The reservoir sits above 2,100m, so pack a layer even on a warm day in Sion.

Before heading out on any cycling adventure check out our Things to Bring on a Cycling Trip and use our interactive check list to ensure you don't forget anything.

The Nendaz valley is a genuine four-season resort area - Super-Nendaz, about halfway up this climb, is a full ski resort in winter and a hiking and mountain-biking hub in summer, with lodging and restaurants if you'd rather base a trip here than in Sion. The chapel of Saint-Barthelemy on the lake's shore is worth a slow look at the top - it's the oldest chapel in the commune of Nendaz, moved to its current spot when dam workers rebuilt it in stone in 1951, with roots as a wooden chapel documented since at least 1447. This climb and the neighboring Barrage de la Grande Dixence climb both start from Sion but head up completely different valleys to two different dams in the same hydro system - worth combining into one trip if you're spending a few days in the area; see our Routes in the Area tool for other climbs nearby.