Ice stalagmites shine in reflected light inside Japan's former Shojingawa mine in Nanae, Hokkaido.

More than 10,000 stalagmites, with some having grown to heights of over 2m, can be found underground in the former iron and sulphur mine, which was closed in 1960.

Water seeping into the mine falls from the ceiling and collects on the floor, forming stalagmites in the below-freezing temperatures.

Experts say that stable winter temperatures inside the mine result in the formation of the ice towers, instead of ice stalactites hanging down from the ceiling.