Eisriesenwelt

The mysteries of Eisriesenwelt were not discovered until 1879. Subsequent exploration revealed that the cave system extends over a total distance of some 26 miles (42 Kilometers). Eisriesenwelt - the "world of the ice giants" - is the largest ice cave in the world. Much of the interior of this cave system high in the Austrian Alps is filled with the fanciful forms of stalactites and stalagmites similar to those found in other caves. But here the contours seem to be more fluid and the colors more translucent. The reason is: The underground formations are composed not of minerals but of ice.
 
Since the temperature in the cave remains at or near freezing all year round, water dripping from the ceiling solidifies into immense icicles, similar to stalactites. Drops falling to the floor freeze, to form spirelike stalagmites. In some places ice stalactites and stalagmites have joined into large floor-to-ceiling fluted pillars. Currently about 200,000 tourists come here every year. The cave with its entrance perched 3,300 feet above the valley floor, is accessible by cable car. Beyond the entrance visitors discover an artfully illuminated, shimmering fantasyland of ice sculptures on a mammoth scale.