Mer de Glace ice cave

The Mer de Glace ice cave (French: Grotte de glace de la Mer de Glace) is an artificial ice cave in the French department of Haute-Savoie, on the Mont Blanc massif of the French Alps. The cave, which is situated within the Chamonix valley, on the Mer de Glace glacier, has been dug out every year since the middle of the 19th century. This annual renewal is made necessary by the flow of the glacier it sits on. Mer de Glace welcomes approximately 350,000 visitors per year.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).