Chamonix is the spiritual home of European mountain running. It is where UTMB starts and finishes; where the Aiguilles Rouges balcony trails offer some of the most accessible high-alpine running on the continent; and where, in late June each year, the Marathon du Mont-Blanc festival turns the whole valley over to the sport for four days.
But the trails are here all summer. This is the guide to both — racing the festival, and running Chamonix on any week you can get here.
The Festival: Five Distances
The 90K The flagship. Roughly 90 kilometres and 6,300 metres of climbing, strung along the valley's high balconies on both sides — the Aiguilles Rouges to the north, the lower Mont Blanc massif trails to the south, a loop out to Vallorcine near the Swiss border and back. A genuine mountain ultra requiring alpine experience, technical descending, and the aerobic base for sustained time above 2,000 metres. Entry is competitive and typically requires prior ultra finishes.
The Marathon (42K) The race the festival is named for. 42 kilometres, ~2,500 metres of climbing, finishing high at La Flégère. The classic Chamonix mountain marathon: a long forest-and-balcony climb onto the Aiguilles Rouges, a high traverse facing the full massif, and an altitude finish. The largest competitive field and the festival's most prestigious win.
The KMV A vertical kilometre — 1,000 metres of ascent over minimal horizontal distance. Short, savage, and won by specialists. The purest climbing test on the programme.
The 23K and 10K The accessible distances. Shortened versions of the balcony routes that put recreational runners on the same trails and views as the elite races. The 23K is a serious half-day mountain effort; the 10K is the entry point.
Running Chamonix Any Week: The Balcony Trails
You do not need a race bib to run the best of Chamonix. The valley's defining trails are its balcons — the high traverses that run at altitude along both walls.
Grand Balcon Nord On the Mont Blanc massif side, accessed from the Montenvers railway or the Plan de l'Aiguille (Aiguille du Midi mid-station). Traverses past the Mer de Glace glacier with the séracs and the Drus directly across the valley. Technical in sections, spectacular throughout.
Grand Balcon Sud On the Aiguilles Rouges side, accessed from the Flégère or Brévent lifts. This is the marathon's terrain — a high traverse with the entire Mont Blanc massif laid out in front of you, from the Aiguille du Midi to the Dôme du Goûter. Runnable, sustained, and the single best view-per-effort trail in the valley.
Aiguillette des Posettes At the Vallorcine end of the valley, part of the 90K route. A ridgeline climb and traverse with views in every direction — the Mont Blanc massif one way, the Swiss Valais the other.
Connect with training partners, earn travel miles, and discover terrain worth crossing borders for.
Join ZealZagFollow us on InstagramThe Lift System
Chamonix's lifts let you trade the climb for altitude or save your legs for the descent: - Aiguille du Midi (Chamonix → 3,842m): the iconic cable car; access to the Plan de l'Aiguille mid-station for the Grand Balcon Nord. - Brévent–Flégère (Chamonix/Les Praz → ~2,000m+): direct access to the Grand Balcon Sud and the marathon's high traverse. - Montenvers railway (Chamonix → Mer de Glace): a cog railway to the glacier and the eastern Grand Balcon Nord.
A Mont-Blanc MultiPass covers the lift network. Many runners climb under their own power and descend by lift, or vice versa.
When to Go
Late June through September is the trail season. Late June (festival time) offers long days, freshly snow-cleared high trails, and wildflowers on the balconies. July and August are peak season — busiest, warmest, with afternoon thunderstorm risk; start early. September brings golden light, thinner crowds, and firm trails, with lifts typically running through late September.
The highest sections may hold snow into early July depending on the winter; check conditions with the Office de Haute Montagne in town before committing to the high balconies.
Getting There
By air: Geneva (GVA) is the gateway — 90km, roughly 1h15 by road. Frequent shared shuttles run Geneva–Chamonix directly. Lyon (LYS) at 220km and Milan (MXP) at 230km are alternatives for specific connections.
By train: The Mont-Blanc Express narrow-gauge line connects St-Gervais-Les Bains to Chamonix and on to Vallorcine and the Swiss border, stopping throughout the valley — useful for point-to-point trail runs.
Getting around: The valley bus (free with most accommodation guest cards) and the Mont-Blanc Express make Chamonix one of the easiest alpine valleys to navigate car-free.
Where to Stay
Chamonix town centre is the obvious base — walkable to the festival start, the lifts, and the trailheads. Range from hostels and the famous climber's institution dorms (€30–50) to alpine hotels (€150–300+).
Les Praz de Chamonix (3km up-valley) sits at the foot of the Flégère lift — quieter, with direct Grand Balcon Sud access. Argentière (8km) is the high-valley base, closer to the Aiguillette des Posettes and the 90K terrain. Les Houches (down-valley) is more affordable and family-oriented.
Book months ahead for festival weekend and for the UTMB week in late August — the valley fills completely.
Mandatory Gear (Festival Races)
The longer festival races enforce mountain safety kit at bib collection — typically a waterproof jacket, survival blanket, whistle, headlamp (for the 90K), food reserve, and a charged phone. Poles are allowed and widely used; the climbs and technical descents reward them. A grippy, rock-capable trail shoe is essential for the balcony single track.
Training for the Marathon du Mont-Blanc
Vertical volume: The marathon's 2,500m and the 90K's 6,300m demand specific climbing fitness. Build sustained uphill work — long climbs, not just intervals.
Technical descending: Chamonix descents are long, rocky, and steep. Untrained quads fail here first; prioritise downhill volume.
Altitude: Sustained running above 2,000m is harder than the numbers suggest for sea-level athletes. A pre-event acclimatisation window helps for the 90K especially.
Local Tips
Eat: Savoyard mountain food is the post-run reward — tartiflette, fondue, raclette, diots (Savoy sausages) with polenta. La Calèche and Le Bistrot in town are reliable. For coffee and pastries before a dawn start, the bakeries on Rue du Docteur Paccard open early.
The non-running day: Take the Aiguille du Midi cable car to 3,842m for the "Step into the Void" glass box and the closest you can get to the Mont Blanc summit without a rope. Or ride the Montenvers railway to the Mer de Glace.
Recovery: The QC Terme Chamonix Mont-Blanc spa is built for exactly this — alpine thermal pools after a day on the balconies.
Frequently Asked Questions
How hard is the Marathon du Mont-Blanc compared to a road marathon? Far harder. With ~2,500m of climbing and an altitude finish at La Flégère, it is a true mountain marathon — winning times are well over three hours, and the terrain, not the distance, is the challenge.
Do I need alpine experience for the 90K? Yes. The 90K is a serious mountain ultra with sustained high-altitude terrain, technical descents, and long exposure. It is not a first ultra.
Can I run the festival routes outside of race weekend? Yes — the Grand Balcon Sud (the marathon's high traverse) and the Aiguillette des Posettes (90K terrain) are public trails open all summer. The lift access makes them among the most accessible high-alpine runs in Europe.
When does registration open? Annually via montblancmarathon.net, typically in the winter preceding the race, with high demand for the marathon and 90K.
For this weekend's race coverage, see our Marathon du Mont-Blanc 90K opening day field report. For the Dolomites' equivalent ultra running this same week, our Lavaredo 120K course guide covers the night-start race from Cortina d'Ampezzo.