Cosmiques Arete to Mont Blanc Traverse: Full Guide, Route Info & Gear List
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Date of Ascent: July 22nd, 2025
Route: Cosmiques Arête + 3 Monts Route (Mont Blanc du Tacul – Col Maudit – Mont Blanc summit – Gouter descent)
Total time: ~21 hours total
Elevation gain: ~1,700 m and descent (3,924 m)
Grade: AD (Cosmiques), PD+ (3 Monts), total route length ~20.77 km
Style: Traverse — light and fast
We took a tram up to Aiguille du Midi around 5 PM on July 21st and spent the night in the Cosmiques hut. Spend the night is a funny term; we took a nap before the alarm went off at 1 AM. Many people say to book far in advance, but we booked the day before in the middle of July and plenty of beds were still available. Click here for prices and booking. It's definitely not a busy hut, or a busy choice of route.
It began, as many alpine days do, with the world still wrapped in darkness.
Chamonix below us slept quietly while our headlamps traced a soft path across the glacier. In a strong snow blizzard, we moved quickly following our intuition on direction. The footsteps have been wiped off by new snowfall and wind. It snowed over 30 cm over the past two days.
We moved across the Vallée Blanche, roped up and quiet.
This was the Cosmiques Arête, one of the most photogenic ridgelines in the Alps, and our gateway to the Mont Blanc traverse. I just wish we took time in between to take some pictures. It was simply too windy and too cold to take off the gloves.
The Cosmiques Arête: Exposure and Elegance
The sun spilled over the ridge as we climbed the final tower. Shadows pulled back from the peaks around us, and the alpine world woke up in golden light. A short rest.
Mont Blanc Traverse: Into the White Silence
The next section—the Three Monts Route—took us up and over Mont Blanc du Tacul, across the Col Maudit, and finally to the summit of Mont Blanc, the roof of Western Europe.
Tacul was steep but straightforward. A long white slope under serac threat, where you move quickly and speak little. On Col Maudit, the real challenge waited: a steep, icy pitch requiring fixed rope and careful footwork in the thin air. Every breath felt measured, every step a negotiation with the slope.
Above, the world turned white and blinding. The cold sharpened. The summit ridge stretched on forever, like a dream you keep waking into. My biggest key to staying dry in the mountains is wearing merino underlayers! BRANWYN Merino is my number #1 choice!! Closing the eyes for a minute and convincing myself I don't feel the headache due to lack of water... and up again.
Then—finally—Mont Blanc. 4,808 meters of quiet triumph.
It’s not dramatic when you reach it. There's no banner, no drumroll. Just damn wind, sky, and a view that silences everything. The Italian side drops steeply away. The French Alps ripple into the horizon. And for a moment, you feel weightless. But just for a moment, since we quickly remembered we have a long way down.
A summit celebration doesn't exist in mountaineering. Not until you're fully safe and on the ground.
The Descent: Humble and Hollow
Summits are never the end.
We descended via the Gouter Route—a long, gradual downclimb past the Vallot shelter and Dome du Gouter, then down the infamous Grand Couloir, where loose rock and melting snow demand full attention.
The legs feel it. The mind drifts. And then, you’re back in the valley—where the air is thick, the ground soft, and people walk around sipping espresso like the sky never almost swallowed you.
01:15 – Cosmiques Hut Departure (3,613 m)
The hut was quiet but electric with pre-dawn tension. We slipped out just after 2.40 a.m., crampons crunching into the frozen crust of the glacier beneath the Aiguille du Midi. Roped up under the stars, we moved steadily toward the base of the Cosmiques Arête, headlamps bouncing off crevassed slopes.
03:15 – Starting the Cosmiques Arête (3,550 m)
We didn't stop to belay, just simo-climbed up.
This section took us just under 2 houra 15 minutes, topping out near the Midi station around 03:30.
05:00 – Transition + Break at Aiguille du Midi
We paused briefly at the Midi col for water and a gear check.
05:30 – Crossing the Vallée Blanche toward Mont Blanc du Tacul
Temperatures were ideal—cold enough to keep the snow solid, with only a slight breeze. We reached the base of Mont Blanc du Tacul quickly, then climbed steadily up its broad north face (~500 m vertical gain). The angle is 35–40°, with some serac overhead hazard.
Tacul summit reached at 07:10 (4,248 m).
07:30 – Col Maudit (4,345 m) – Steepest Section
After a gentle descent from Tacul’s summit plateau, we roped up for the Col Maudit headwall—the crux of the 3 Monts route. This pitch is steep (up to 50°) so we moved extra quick. Especially with all the overhead hazards. Solid ice beneath a crusty snow layer. Short but intense.
We gained the Col and took a proper food break here, starting to feel the effects of altitude.
09:20 – Summit Push from Col de la Brenva (4,303 m) to Mont Blanc (4,808 m)
The final stretch was physically demanding but mentally steady. No technical difficulties—just a long, exposed snow ridge and ever-thinner air. and yeah: 100 kms winds! Brutal...
Mont Blanc Summit reached at 11:30 a.m.
11:45 – Descent via the Bosses Ridge + Gouter Route
We didn’t linger on the summit. After a few photos and deep breaths, we began the descent down the Bosses Ridge, past the Vallot Bivouac (4,362 m), then the Dôme du Goûter.
Snow softened fast in the sun. By the time we reached the Goûter Hut (~2:45 PM), our legs were feeling every meter of descent.
From there we down climbed over 600 meters of snowy and icy via ferrata. As it was getting late we didn't waste time with protection. And half way down we also took our crampons off.
16:30 – Grand Couloir + Final Descent to Nid d’Aigle (2,372 m) + 1000 m down to Los Houches
We crossed the Grand Couloir quickly (watching carefully for rockfall) and made the long, hot descent down the Goûter trail to the Tête Rousse Hut, then continued to the Nid d’Aigle tramway. The train isn't working for the season, so we had to walk down to the village ourselves. Those 1300 m and 10 kms dragged on for another 2.5 hours, almost... coming to Los Houhces village
Packing List: Cosmiques + 3 Monts Traverse
We went light but conservative for the high alpine terrain. Conditions were solid, but serac threat and cold exposure made careful planning essential.
Clothing
- Lightweight softshell pants
- Synthetic or merino baselayer (top and bottom) BRANWYN Merino is my number #1 choice!!
- Midweight fleece or grid hoodie
- Waterproof hardshell jacket + pants
- Lightweight down jacket (summit and rest stops)
- Warm gloves + backup pair: Baist Gloves – Code: “ALENKABaist“
- Thin liner gloves
- Warm beanie + Buff
- Glacier glasses + ski goggles (for summit ridge)
Footwear
- Mountaineering boots (La Sportiva G5 / Scarpa Phantom Tech)
- Crampons (steel, 12-point, with anti-balling plates)
- I didn't bring approch shoes but I would highly recommend them when the train isn't working!
Technical Gear
- Harness
- Helmet
- 40 m glacier rope (twin or dry half-rope)
- 2 ice axes (1 tech + 1 lightweight)
- 3 locking carabiners
- 2 prusiks
- Tibloc or microtraxion (for crevasse rescue)
- 2 ice screws
- 1 snow picket (optional) - we didn't bring this, because we didn't stop to belay in between
- 1 alpine draw + a few slings
- Lightweight glacier rescue kit (pulley, cord, carabiners)
Miscellaneous
- Headlamp + spare batteries
- Suunto watch with altiman eter
- Glacier sunglasses, we used goggles
- Topo printout + GPX on phone
- Sunscreen + lip balm
- Energy gels/snacks + hydration tablets
- 1L water bottle + 0.5L thermos (not that we drank that much but we should've)
- Emergency bivy or foil blanket, because you never know
🧭 Notes + Tips
- Start early: Weather and snow conditions shift fast on this route. We postponed our departure from Cosmiques Hut to 2.40 AM and I wish we left earlier (like 1 AM) - save your energy for the descent if you're planning on doing it in 24 hours
- Serac awareness: Both the Tacul face and Col Maudit are under icefall danger. Move efficiently and don’t stop under overhead hazards.
- Altitude: The route gains altitude quickly—consider acclimatizing on Aiguille du Midi or spending a night at Cosmiques before heading up.
- Fitness: This route is not overly technical, but it’s long. Stamina and comfort on exposed terrain are essential.
Final Thoughts
The combination of Cosmiques Ridge and the 3 Monts Traverse makes for one of the most aesthetic and rewarding alpine days in the Alps—technical enough to stay focused, and not think about the altitude.
And when you descend, sore and sunburnt and silent, you'll know it was worth every step.
What I would do differently on the Cosmiques Route on Mont Blanc:
I would probably descend via the Cosmiques route again. Even though it's steep, it's a lot shorter than the grueling Gouter route descent. Only note, if you do want to do that, you have to make sure you're back by 5 PM on Aiguille du Midi to catch the last tram to Chamonix. Otherwise, you have to spend one more night in Cosmiques hut, and it can get expensive.
I would also accimatize a little better next time. Maybe spend an extra day in Chamonix or climb up 3000 m overnight, and then go back down before doing Mont Blanc. Even though the altitude didn't affect us too badly, we still moved more slowly because of it I think.
I would bring approach shoes!!
Reflections from the Ridge
I can't wait to return to Mont Blanc and fly off! Save myself the gruoling descend ;)
Questions? Post below or get in touch directly. Happy to help!
— Alenka