Mer de Glace and the Montenvers train: ice cave, prices and glacier retreat
Written by Victor Michel — history enthusiast and passionate alpinist based in Chamonix. Publié le 16 juillet 2026
The Mer de Glace is France's largest glacier, over 7 km long, visible from the Montenvers site (1,913 m) above Chamonix. A rack railway has reached it since 1908-1909, and an ice cave is carved there anew every year. The staircase leading to the cave grows longer each year, making the glacier's retreat visible.
À retenir
- France's largest glacier: over 7 km long, Montenvers site at 1,913 m
- Rack railway from Chamonix: opened in 1908 (first section), completed in 1909, 5.1 km of track, 871 m elevation gain
- Ice cave carved anew each year directly into the glacier
- 2026 prices: from €31.50 (train round trip only) to €68.40 (hike + ice cave package)
What is the Mer de Glace?
The Mer de Glace is France's largest glacier, over 7 km long, fed by the slopes of the Mont Blanc massif (including the Géant glacier). It is viewed from the Montenvers site, at 1,913 m altitude, reachable with no technical gear by rack railway from Chamonix.
The Montenvers train: a century-old rack railway
Construction of the line began in 1906; a first section opened in 1908, the full line in 1909. The 5.1 km track climbs 871 m of elevation via a rack-and-pinion system (a toothed center rail), up to the Montenvers site at 1,913 m — a historic viewpoint over the glacier for over a century.
The ice cave: a sculpture rebuilt every year
A gallery is hand-carved each year into the glacier's ice, reached by gondola and then a staircase whose number of steps increases as the glacier retreats and its surface lowers. The cave usually opens later in the season than the train, once the new galleries are finished.
Glacier retreat, visible to the naked eye
The Mer de Glace loses thickness and retreats every year, a phenomenon documented by the gradual lengthening of the staircase leading to the ice cave from the gondola station. This measurable retreat makes it a reference site for observing the evolution of alpine glaciers first-hand.
| Package | Adult | Child (5-14) / senior | Family |
|---|---|---|---|
| Train only (one-way) | €26.50 | €22.50 | — |
| Train only (round trip) | €31.50 | €26.80 | €97.70 |
| ALPI Pass (train + gondola round trip) | €43.30 | €36.00 | — |
| Mer de Glace journey (train + gondola + ice cave) | €49.70 | €42.20 | €148.30 |
| North Balcony (train + gondola, hiking) | €48.40 | €41.10 | — |
| Complete package (hiking + ice cave) | €68.40 | €58.10 | €212.00 |
À lire ensuite
FAQ
How long is the Mer de Glace?
Over 7 km, making it France's largest glacier. It is fed by several glaciers of the Mont Blanc massif, including the Géant glacier.
Since when has the Montenvers train existed?
Construction began in 1906, a first section opened in 1908, and the full line in 1909. It is a 5.1 km rack railway climbing 871 m of elevation up to the Montenvers site, at 1,913 m altitude.
How much does visiting the Mer de Glace cost in 2026?
From €31.50 for the train round trip alone, up to €68.40 for the complete package including the North Balcony hike and the ice cave visit. The "Mer de Glace journey" pass (train + gondola + cave) costs €49.70 per adult.
What is the ice cave?
A gallery hand-carved each year directly into the glacier's ice, reached by gondola and then a staircase. It usually opens later in the season than the train, once the new galleries are finished.
Why does the staircase to the ice cave get longer every year?
Because the glacier is losing thickness and retreating: its surface lowers year after year, requiring extra steps to keep reaching the ice from the gondola station.
Can you visit the Mer de Glace without mountain experience?
Yes. The rack railway, gondola and ice cave are accessible to everyone, with no technical gear. A hiking trail (North Balcony or Grand Balcony North) also reaches the site on foot for more experienced walkers.
What is the best time to visit the Mer de Glace?
The ice cave is generally accessible from June to September, once the new galleries have been carved. The train runs over a wider period, with reduced winter service.