Voie Communale N°1, 74400 Chamonix-Mont-Blanc, France
The 7km (4.3 mile) long glacier Mer de Glace was named as such (it translates to "sea of ice") by 18th-century explorers. The ice plane has been slowly shrinking over the past few centuries and is currently the lowest it has been since Medieval times. There are caves formed from the ice that can be explored but the best view is from the Montenvers outlook, reachable by train (a 20-minute journey from Chamonix center). Stay for lunch or a snack at Hotel Restaurant Montenvers. During the ski season the Mer de Glace is skiable as part of Vallée Blanche.
Written by Amelia Osborne Scott