Photo: Greenish tinge from the sculptures inside the Ice Palace in Jungfrau

These are sculptures made of ice inside the Ice Palace (ice tunnel) at the Swiss mountain resort of Jungfrau. Varied sculptures, they looked very beautiful with a greenish tinge all around (the light being greenish because of the ice all around us). I always wondered as to how they ensure that the ice remains, and if this tunnel is a part of a glacier, how can they ensure that there is no movement of the ice.