Alpe d’Huez is a terrible climb. It’s still enjoyable if you’re into that sort of thing, but it’s extremely monotonous, and a prime launchpad for watt-watching efforts. I truly believe you can get much the same experience by riding Alpe du Zwift and using your imagination. Without the throngs of fans by the roadside it feels sterile, not aided by the aspect, meaning it gets baked by the afternoon sun in its entirety. It’s far better to ride down the Alpe, and ride up the Col de Sarenne instead.
The lesser known back way to the Alpe d’Huez ski resort is being used as an ascent for the first time in the Tour de France this year, as the penultimate ascent on stage 20 this Saturday. The stage is a beast, 170km in length with the Col de la Croix de Fer, the Col du Télégraphe and the Col du Galibier all coming before the hors catégorie Sarenne in the final 25km.
The Col de Sarenne was last used in 2013 as a descent, complete with hastily-added hay bales after much consternation about the danger the route presented. In order that you may be familiarised with this new col, I spent a hot afternoon in June riding it, on a beautiful loop from Alpe d’Huez and back.
It is a truly sensational climb. A real climber’s climb: narrow, undulating, with distinct phases and spectacular views. There are some horrible pitches that are hidden by the stats: 12.8km at 7.5% sounds easier than the Alpe’s 14km at 8%, but the Sarenne pitches up to 14% for its steepest 100m stretch, and its final 4km are at 9%, with the ultimate hairpins pitching up to 12% just to wring every joule of energy from your legs. I loved it, and I massively underestimated it.
Image 1 of 4
(Image credit: Will Jones)
(Image credit: Will Jones)
(Image credit: Will Jones)
(Image credit: Will Jones)
Softening up
My route up the Sarenne began differently to that which the Tour will trace, based as I was in Alpe d’Huez for some other work engagements. While the Tour heads down the more or less totally straight valley road from La Grave, I came at it from Bourg d’Oisans. After an arrow-straight highway, descending to deprive you of precious metres of elevation, you enter the belly of the beast via a spectacular gorge, split by a river and a large Alpine highway.
The climb
- 12.8km at 7.3%
- Reaches an altitude of 1,999m
Two very manageable ramps get you to Mizoen when the climb begins, but from my point of view, with an ascent of Alpe d’Huez in my legs from the day before, I was glad things weren’t too severe to begin with. This way is you get two short descents and a couple of refreshingly cool tunnels to steady the ship before things begin in earnest. You also get to see the full height of the dam that holds back Lac du Chambon, which you then have to ride across. Don’t look down, but don’t look up either as things head relentlessly skywards from here on in.
Dam busters
The Sarenne begins in earnest just after the dam. You’re faced with a rusty, cubist building overlooking the expanse of water, at which point you turn left and have to tackle three ramps up to Mizoen, all over 11% and topping out, according to my Strava trace, at just over 13% on the initial pitch. It’s a very sustained 2km of effort, and while it’s very early in the climb to act as a launch ramp if the race is still together, it will reveal very early who has the legs.
These ramps also mark a distinct change in feel – from here on in it feels much more Pyrenean than Alpine.
Mizoen and the kilometre beyond it offers the first of two places to get some life back into your legs or, in the case of a race, a prime place to pick up a willing satellite domestique for a tow if the stars align. The end of this relatively flat stretch is marked by a short, sharp descent which slingshots you into another pair of ramps and hairpins, the first of which tops 15% before sending you onwards on a proper full width, two lane road to Clavans-le-Bas.
Mizoen to Clavans-le-Bas is certainly the least interesting part of the ascent. A larger road, surrounded by nondescript woodland that hides what’s to come. From Clavans-le-Bas comes the second, longer section of flat-ish (2-3%) for about a kilometre and a half past grazing cows (at least when I did it) and a very timely eau potable sign with a trough to soak my sun-addled head before things really get serious.
Image 1 of 3
(Image credit: Will Jones)
(Image credit: Will Jones)
(Image credit: Will Jones)
The woodland zone
From Clavans-le-Bas to the summit there is no let-up, but the scenery is divided neatly into two parts. The first wends its way through beautiful woodland, with Alpine flowers blooming in every verge. I’m not too proud to admit I was in the box a little bit at this point, and so didn’t take any photos. My one memory, besides thinking ‘Hell, this is hard work’ is that I imagined the honey from here would be really excellent; I expect I was craving sugar.
The woodland does offer welcome shade before what is quite an exposed final section, but with that comes a stillness and a noticeable increase in humidity, not aided by the numerous roadside streams, which occasionally spill out onto the road.
From the woodlands and beyond the road surface is markedly terrible. The road is wide enough for a single vehicle, and terribly pockmarked. Patches of fresh, unset bitumen sprinkled with gravel are dotted every few metres, and cause immediate wheel slip out of the saddle, and cause hitchhikers to cling to your tyres. It’s not a descent I would relish, even as someone who usually cherishes Alpine descents. Given the increased focus on rider safety these days, I think if the route had gone down the Sarenne again this year there would have been uproar.
A giant boulder and the final ascent
The problem with the woodland, pretty though it is, is that there is a lot left to the imagination. It feels placid amongst the trees, secluded but not lonely and isolated. If, like me, you have the elevation profile on your computer you’ll be left wondering when things will change. Abruptly, signposted very easily for anyone watching the race on television, the treeline gives way at a stone house perched under a comically large boulder. It’s an obvious metaphor, but from here on in you are the house, and the mountain is the boulder.
The upper slopes of the Sarenne are exposed, oppressive, and considering you’re only a handful of kilometres, as the crow flies, from the relatively large Alpe d’Huez ski resort, they feel extremely isolated. Even compared to the single lane up the Col d’Aspin in the Pyrenees it feels ancient. It doesn’t impose with grandeur in the same way as the upper reaches of the Col de l’Iseran, it’s much prettier than that, but there is the same feel of being totally out of reach.
The main issue, beyond the gradient which never lets up and the surface which is truly awful, is the fact you can now see the top, and the ten hairpins that lie between you and the end. The first six come in quick succession, but the central portion of much longer straights and fewer hairpins is much more mentally challenging. I was glad to have to stop and take photos at this point.
Four kilometres from the top is where the trees give way, and it’s a real grind. From a race perspective anyone who is dropped here will be able to see the race slipping away from them for almost the entirety of the rest of the way, sapping morale still further. The final couple of hairpins are short, steep, and spit you out onto what feels like a false flat for the last few hundred metres to the high point.
Unlike the climb to Alpe d’Huez, which doesn’t seem to finish anywhere but rather diffuses into an ugly resort leaving you without any real sense of achievement, the Sarenne does at least offer a definitive finish point. It’s nondescript, marked with a sign and a modern triangular hut next to some concrete ruins, but it is a finish line nonetheless and extremely welcome.
While the peak ends here, the stage does not. Like me, riders then have to descend down the balcony road to Alpe d’Huez before tackling a few final hairpins to a finish line that feels a little manufactured, especially given it will have hosted a finish just 24 hours previously. Logistically it makes sense, but from a drama perspective I’m not so sure. The descent to the resort is beautiful, but far from flat and in dire need of resurfacing, or in some places just surfacing; it’s gravel, in places, and offers a taste of the danger of what descending the Sarenne would be like.
The world’s biggest bike race deserves world-class coverage. Subscribe to Cyclingnews for unlimited access to our unrivalled reporting of the 2026 Tour de France. From Barcelona through to Paris, our experienced team will bring you breaking news, expert insight, and in-depth coverage from every stage as the battle for the yellow jersey plays out. Plus, access the Cyclingnews app to follow the action on the go! Find out more.