The Iseran is an incredibly long climb. From Bourg-St.-Maurice, it takes no less than 48 kilometers.
Luckily the percentages are not too high and there are even some long descents to recuperate.
The Col de L'Iseran is one of the biggest climbs in France and from the Tour de France. Well deserved, although you wouldn't suspect that after the first part, up to the reservoir. You have to go through here to get to the real climb, which is magnificent. It's definitely a climb that has to be on everyone's bucket list.
From Bourg-St.-Maurice take the D902 to Sainte-Foy-Tarentaise. Soon you drive along the river Isère which will follow you almost to the top. Only after Sainte-Foy-Tarentaise follow some heavier stretches and flirt the climb with " yellow " (+ 7%). After 15 kilometers you'll reach La Thuile, after which the climb becomes a bit calmer again on annoyingly long straights. After passing the first exit towards Tignes (D87B) six kilometres further, the climb becomes more difficult again until you see the imposing dam of the reservoir on your right. What follows are 9 almost flat, sometimes even descending, kilometers to Val d'Isère. Pay attention and be sure to take some light with you on your bike, because here are only dark, narrow and therefore not very safe tunnels.
From the beautifully situated ski village of Val d'Isère the climb begins, after 33 kilometers really. What follows to the top belongs to the more beautiful climbing. Only now you see the actual Iséran. After the Pont-Saint-Charles it gets a lot steeper again. You are now at over 2,000 meters altitude and that crawls in the legs. In a little while you get a view on Val d'Isère with behind it, the Lac de Chevrvil. A few hairpin bends offer a welcome break. Between boulders, snow or remnants of snow, the climb back to the end becomes a bit easier. But after a few hours of climbing it is well deserved. Eventually you'll get to see the famous chapel at the top as well as a souvenir shop where you can refill things. In front of you is the snowy summit of the Grande-Sassière, almost 4,000 meters high.
The best part might follow, at least, if you drive on to Bonneval. If not, take the trouble to continue for a kilometre. After all, what follows is one of the most beautiful mountain ranges in the Alps.