Ice forms in summer and melts in winter inside this cave. Pressure-induced phase changes reverse normal seasonal patterns creating permanent ice at low elevation.
CC BY-SA 3.0, via Wikimedia Commons
The chimney in the mountain
Eisriesenwelt, "World of the Ice Giants" in German, is the world's largest ice cave, with a surveyed length of over 42 kilometers. It is a dynamic cave; its its internal climate is actively driven by the temperature difference between the inside and the outside. The cave system has openings at different elevations within the Hochkogel mountain, which creates a natural ventilation system known as the "chimney effect."
In winter, the air inside the mountain is warmer and less dense than the frigid air outside. Cold, heavy air flows down into the lower cave entrances, displacing the warmer air which rises and exits through higher openings. The process chills the lower sections of the cave to below 0°C. In spring, meltwater from snow seeps through cracks in the limestone. When this water reaches the supercooled parts of the cave, it freezes, forming the immense ice structures.
During summer, the opposite occurs. The air outside is warmer than the cold, dense air settled inside the cave. This heavy internal air effectively creates a "cold air dam," preventing the warmer air from penetrating deeply. A cold wind blows out of the cave entrance. Any warmer air that does enter is rapidly cooled, and its moisture condenses and freezes, adding new layers to the ice formations. The ice therefore appears to grow in the summer.
Melting under pressure
The weight of the ice itself introduces another physical process. Some ice formations, like the Great Ice Embankment, reach a thickness of 25 meters. This enormous mass exerts high pressure on the ice layers at the very bottom. Water is an unusual substance; unlike most materials, its melting point decreases as pressure increases. At the base of these thick ice formations, the pressure is sufficient to lower the melting point to just below the ambient cave temperature.
This phenomenon, known as pressure melting, causes the ice to melt at its base even when the cave's air temperature is below freezing. The resulting meltwater can then flow to other parts of the cave and refreeze, adding to the dynamic and ever-changing nature of the cave. Analysis of the ice layers suggests the oldest ice in the cave is approximately 1,000 years old. The cave itself began forming around 100 million years ago as the Salzach river and millennia of water erosion carved passageways through the limestone of the Tennengebirge mountains.
💡Fun Facts
The cave was officially discovered in 1879 by Anton Posselt, a naturalist from Salzburg, who explored the first 200 meters.
Speleologist Alexander von Mörk, who conducted expeditions in 1912, gave the cave its name, "Eisriesenwelt," based on the Norse saga of Thor's journey to the giants.
The public tour covers the first kilometer of the cave, the only section permanently covered in ice. The rest of the 42-kilometer system is bare limestone.
A tour involves climbing a vertical distance of 134 meters, equivalent to the stairs in a 40-story building.
Daily from early May to early November. The first tour is around 9:30 AM and the last is around 3:45 PM. It is recommended to book tickets online for a specific time slot to avoid waiting.
Admission
A combination ticket for the cave tour and mandatory cable car costs approximately €41-€45 for an adult, with discounts for youth and children.
Accessibility
The journey requires a 20-minute walk to a cable car, the cable car ride, and another 20-minute walk to the cave entrance. The tour inside is not wheelchair accessible and requires climbing many stairs. Warm clothing and sturdy shoes are necessary, as the internal temperature is around 0°C (32°F).
