Inside a limestone mountain in the Austrian Alps, 42 kilometres of caves are decorated with permanent ice formations — cathedrals and pillars of frozen water that have existed for thousands of years.
Eisriesenwelt means World of the Ice Giants. The name was assigned by the speleologist Alexander von Mörk, who first explored it extensively in the early 20th century. He was correct. The caves are a world — 42 kilometres of passages, galleries, and chambers, the largest ice cave system on Earth, extending deep into the Tennengebirge massif above the Salzach Valley.
The ice forms in the first kilometre of the cave system and extends through a labyrinth of passages that local guides take visitors through by acetylene lamp. The physics that create it are specific: in winter, cold air flows into the cave and chills the rock. When spring meltwater enters through cracks in the mountain above, it freezes on contact with that chilled rock, building the ice formations year by year. In summer, the airflow reverses and warm air enters — but the rock stays cold, maintaining the ice.
The formations are not stalactites and stalagmites of the usual kind. These are structures of pure ice: columns of frozen water two storeys tall, walls of translucent blue-white ice, frozen waterfalls suspended in mid-flow. The largest chamber — the Posselt Hall — is roughly 100 metres across. The Hymir''s Castle formation reaches 25 metres in height.
Von Mörk himself is entombed in the caves. He died in World War I on the Italian front, and his ashes were brought back by his colleagues and placed inside the cave system he gave his life exploring.