Grenoble, the capital of Isère, has hosted numerous stage finishes and decisive time trials that have reshaped the general classification. Riders such as Merckx, Hinault, Indurain, Armstrong, Contador and Froome have all passed through, forging – or losing – their place in history.

What truly sets Isère apart is its exceptional concentration of legendary climbs: Alpe d’Huez, the gateway to the Galibier and the Lautaret, the Glandon and the Croix de Fer. These are names that resonate with cycling fans around the world.

13.8 km, average gradient 7.9%

The 21 bends of Alpe d’Huez

Undoubtedly one of the most famous mountain passes in the world. From Le Bourg-d’Oisans, the 21 hairpin bends follow one after the other. The first few kilometres have a gradient of over 10 per cent, before levelling off at around 8–9 per cent all the way to the summit. The climb ends at the resort of Alpe d’Huez, at an altitude of 1,860 metres.

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12.8 km, average gradient 7.3%

Col de Sarenne

The least-known of the Isère mountain passes is one of the wildest. The road climbs from Le Bourg-d’Oisans through rocky landscapes of austere beauty, far from the hustle and bustle of the major climbs. The Col de Sarenne had its moment in the spotlight in 2013, during the 100th Tour de France, when it linked two ascents of Alpe d’Huez in a single stage.

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27.5 km, average gradient 4.7%

Col de la Croix de Fer

Don’t be fooled by its average gradient: it is the uneven terrain over nearly 30 kilometres that makes the Croix de Fer such a formidable challenge. The climb up the Isère side offers ever-changing scenery: waterfalls plunging towards the valley, the Grand-Maison dam nestled between the peaks, then the Aiguilles de l’Argentière rising up in the final third.

The road, built in the 1930s, reaches the summit at 2,067 metres, where the metal cross that gave the pass its name stands. It has featured in the Tour more than 20 times since 1947.

29 km, average gradient 5.1%

Col du Glandon

A silent sentinel overlooking the Eau d’Olle valley, the Glandon is one of the most feared passes in the Oisans. Its length and the gusts of wind at the summit make it a pass in a class of its own. The ascent from Allemond gradually takes riders through the various alpine zones: coniferous forests, mountain pastures, and finally the barren, rocky summit.

The pass has been crossed on several occasions during key stages of the Tour, often as a prelude to Alpe d’Huez, in stages that have shattered the peloton.

12.5 km, average gradient 5.6%

Col d’Ornon

Less spectacular in terms of altitude than its neighbours, the Col d’Ornon is the unassuming gateway between the Oisans and the Matheysine. Entirely within the Isère department, it winds through pastoral landscapes of rare beauty, between high-altitude meadows and views of the Écrins. Its appearance in the Tour de France is more sporadic, but it is one of those ‘linking’ passes that play an important tactical role in long Alpine stages.
In summer, it is regularly closed to cars for hill climbs, much to the delight of cyclists.

12 km, average gradient 6.8%

Col de Porte

On the outskirts of Grenoble, nestled beneath Chamechaude – the highest peak in the Chartreuse range – the Col de Porte is one of the oldest mountain passes crossed by the Tour de France. As early as 1907, during the 5th stage between Lyon and Grenoble, the peloton climbed its slopes, making it, for a brief moment, the ‘roof of the Tour’. The climb from Grenoble features gradients of over 10 per cent in its first section, before levelling off towards Sappey-en-Chartreuse. The descent on the north side plunges towards Saint-Pierre-de-Chartreuse through pine forests, offering breathtaking views of the surrounding landscape.