The Mer de Glace and the Montenvers mountain train are one of the main attractions of the Chamonix Valley. The Mer de Glace, or Sea of Ice, is a gigantic glacier moving at a pace of around 120 meters per year. One of the main attractions of the Mer de Glace is the Grotte de la Mer de Glace. This is a large man-made ice cave with carvings, statues and light effects. This is a very unique experience that should not be missed. There aren't many places in the world where you can enter into a glacier after all. 

In winter, the Mer de Glace is part of the very famous Vallee Blanche skiing route starting off at the Aiguille du Midi and ending at the bottom of the Mer de Glace. Unfortunately, with global warming, the glacier is retreating at a rapid pace. Markings on the rock walls on the side of the glacier show the level that the glacier used to be in years past. It is shocking how fast the level is getting lower and lower and the ice cave and its entrance have had to be moved lower and lower as well as a consequence. 

The Montenvers mountain train gives easy access to the Mer de Glace. From there is easy to continue onward and do one of the most popular trails in Chamonix: the Grand Balcon Nord to Plan de l'Aiguille. If you don't want to take the train then the Montenvers mountain station and the Mer de Glace can be reached using a trail from Chamonix.