You are going to see the Ruskeala Marble Canyon on these photos. It is located in Karelia, Russia. The thin ice lies under the the layer of sleet and water. This place is a nice way to find yourself in a winter fairy-tale.
The Marble canyon formed in the 1960s during the collapse of the mine gallery. The diameter of the hole which appeared there was 20-30 meters (65-100 ft). In summer the hole is filled with water, in winter one can safely go down to see such a beauty.