Insights behind the scenes in the natural ice palace Tyrol

At the mountain station of the Hintertux Glacier, at 3250 meters above sea level is the final stop. Austria's year-round ski area is located here. However, we have to postpone the popular panoramic view until later. It's storming today and visibility is zero. But the natural ice palace is also a perfect destination during a storm. As long as the stable gondolas of the Zillertaler Gletscherbahn are in operation, adventure awaits.

With no wind, at a constant zero degrees Celsius and up to 35 meters below the ski slope, the natural ice palace offers a glimpse of a fantastic ice landscape. Stairs and ladders lead visitors through icy corridors and halls with different levels, meter-long icicles and an underground glacial lake.

• Of snow groomers and avalanche probes
• Discovery of the Nature Ice Palace
• Deepest glacier research shaft

• Underground glacial lake
• World records in ice swimming
• Curved Ice Pillars

From heavy snow groomers and avalanche search probes

But today we first seek refuge in the small, heated container at Natursport Tirol. While we wait for the natural ice palace to open its doors for us, we look forward to exciting stories. Insights behind the scenes and first hand.

Mr. Erler is in contact with his employees via radio. "We have to clear the way first," he informs us. Today the boys are up to their chests in fresh snow and are making their way to the entrance. With a smile he adds: "That's just a pinch of snow". With fresh snow and storms, snowdrifts ten meters high can quickly form and bury the entrance. Access to the Natural Ice Palace is often shoveled free again with heavy snow groomers. Sometimes the entrance hall has to be searched for with an avalanche probe, and every now and then a blast is even necessary to break through the snow masses.

Preserving the Ice Cave is more involved than we thought. "Glacier cave", corrects Mr. Erler. What is somehow the same for the layman is an important difference for the expert. An ice cave is a rock cave in which there is permanent ice. A glacial cave is a cave in glacial ice.

A fantastic coincidence: The discovery of the natural ice palace

Roman Erler discovered the Natur-Eis-Palast in 2007 by accident. This can be read in numerous articles and also on the website of "Natursport Tirol", Roman Erler's family business. But how should one imagine this coincidence? Did he go for a walk and then suddenly stood in front of the entrance? No, it wasn't that easy after all. As the old saying goes, luck favors the brave. And that's how it was here, because without an extra portion of attention, knowledge and commitment, the natural ice palace would never have been discovered.

"Slope no. 5 in the Hintertux Glacier ski area was the steepest slope with no known crevasses," recalls Mr. Erler. Actually, that's illogical. Because of the glacial movement, there should have been crevasses there. Then, in August 2007, he suddenly noticed a 10 cm gap in the ice wall that had never been seen before. Others rushed by without heeding it, but his interest was piqued. "I've found quite a few things by accident," laughs Roman Erler.

The people of Zillertal are very familiar with glaciers. As a mountain rescuer, he has also had to rescue people from a crevasse. So he returned with his gear and climbed to this newly visible crevice. In the light of his flashlight, the inconspicuous gap opened up surprisingly generously. How big was the cavity behind it? The discoverer then opened the crevasse with a compressed air device for clamping crevices.

At first it was also about whether winter sports above the glacier cave are still safe. Normally you pull people out of a crevasse. It was not initially planned to lead people into this glacial cave.

The deepest glacier research shaft in the world

Roman Erler not only discovered and opened up the natural ice palace, he also drove the deepest glacier research shaft in the world to date into the Hintertux Glacier. Personally and over several years. Roman Erler pre-drilled every millimeter. "With a 12mm 80cm masonry drill," he says, his eyes shining. "And that was a good thing." Once, while pre-drilling, he suddenly dropped with the drill bit. He had drilled a cavity with water and compressed air. It hissed and then a meter-high fountain of ice water shot towards it.

After that the shaft was under water. It took a while before it was pumped empty again, but it worked. Previously unknown and water-filled corridors branching off from the shaft were also drained. Untouched and an exciting place for research. The reward is new insights into the structure and dynamics of the glacier. Today the research shaft reaches down to the ground. It is 52 meters deep and starts about 20 meters below the surface. The shaft is around 3 meters wide in the upper areas and around one meter in diameter at the bottom. Tourists can also take a look inside during a guided tour of the Natural Ice Palace.

A sporting feat: In December 2019, the Austrian Christian Redl set a new world record in freediving in this shaft. In ice water at minus 0,6 °C and at an altitude of 3200 meters, he dived 23 meters deep with just one breath.

An underground glacial lake

The glacial lake in the Natural Ice Palace is around 50 meters long and up to 22 meters deep. Many administrative procedures were necessary before the boat trip for tourists was approved. The lake is in the middle of the glacier, around 30 meters below the ski slope, surrounded by ice. "Perhaps you can imagine what was going on there," says Roman Erler, and the enthusiasm for his project is written all over his face.

The water is crystal clear. Depending on the incidence of light, it looks dark or turquoise blue. A tunnel of ice stretches above it. Reflection and reality combine almost seamlessly. Beautiful. Unique. Fascinating. But are you sure? We want to know more and ask: "Does the height of the lake change due to rain or meltwater?" "Could it then be dangerous?" Mr. Erler can reassure us. There is an overflow.

But how did this unusual lake come about? We have already learned that the Hintertux Glacier is a cold glacier. This means that its ice temperature at the bottom of the glacier is so well below zero degrees Celsius that there is no longer any liquid water there. The glacier floor of this type of glacier is therefore watertight. Liquid water collects in crevices above this area. This is how this glacial lake was formed.

However, when it was discovered, the canal was completely under water. Roman Erler's team broke away part of the ice and created an overflow. This has regulated the water level. Now visitors can marvel at the glacial lake in a rubber dinghy or while doing stand-up paddling. As an exception, permits for scuba diving are also issued, says Roman Erler. Last week, divers from the fire department were in the glacial lake.

World records in ice swimming

While scuba diving remains an exception, ice swimmers are almost the rule in the Natural Ice Palace. "It's hard to believe how many ice swimmers there are," muses Mr. Erler. He now knows the best of the best.

In 2021, Josef Köberl swam 1,5 kilometers in 38 minutes in the glacial lake of the Natur-Eis-Palast. Shortly before the desired ice mile (around 1609 meters), however, Josef Köberl had to break off to avoid life-threatening hypothermia. Still, an outstanding achievement. In December 2022, he was then surpassed by the Polish ice swimmer Krzysztof Gajewski, who set a new and extraordinary world record in ice swimming in the Natur-Eis-Palast: The Pole reached the ice mile after 32 minutes and then swam even further. In total, he swam for 43 minutes in the Hintertux Glacier and covered a distance of 2 kilometers.

Curved Ice Pillars

Another exciting phenomenon that visitors to the Natural Ice Palace can experience up close today is how ice reacts to pressure. Ice seems unstable and fragile to us. If you put pressure on an icicle, it'll break, right? On the tour of the Natural Ice Palace you will see that this assumption is wrong.

The Hintertux Glacier is not static. But everything that happens happens in a kind of extreme slow motion. And in this case, the ice does not react to the pressure from above by breaking, but by deforming. Fantastic ice sculptures are the result. Curved ice pillars, deformed icicles and twisted ice artworks from the hands of Master Nature himself. Come in and be amazed is the motto. "We have a research assignment and an educational assignment," says Roman Erler. And you can tell that he takes both very seriously.

More than a kilometer of the subterranean passages of the glacier cave have now been measured and documented. 640 meters of it are accessible to tourists. Since 2017, the so-called Jubilee Hall has also been open to tourists. This is particularly richly decorated with meter-long icicles and ceiling-high ice formations. A dream of ice!

Behind it are two more rooms that are not yet open to the public. They are currently used exclusively for research. When we asked whether the glacier cave had been fully explored in the meantime, Roman Erler answered with a resounding "no". More cavities are known but not yet explored. So many a surprise is still slumbering in the Natural Ice Palace today.

Is global warming an issue?

We are worried, but Roman Erler reacts calmly: "There is no less ice up here than in the Ice Age". The heart-blood glaciologist spontaneously blossoms into a hobby historian and we learn that there are many exciting entries about the Little Ice Age in the village and church chronicles. At that time, the concerns of the residents were quite different. The glaciers advanced. It snowed in the summer. The cattle could not be driven up to the pasture and they died. There were famines.

Since then, the climate trend has changed again. It is currently getting warmer in Tyrol and the first changes are noticeable in the valley. But there is also good news: "In the Zillertal there are two hanging glaciers that are advancing slightly," says Roman Erler. Against the trend, which indicates an overall melting of the glaciers.

Thanks to the altitude of up to 3250 meters, things are currently looking good for the Hintertux Glacier. But isn't there less snow here due to the mild winters? "On the contrary," explains the expert. Mild winters mean more precipitation, so more snow for high-altitude areas. However, hot summers have a negative effect. "The best thing for the glacier would be a mild winter and a mild summer," explains Roman Erler.

In addition to its altitude, the Hintertux Glacier has another advantage over many other glaciers in the Alps. It is a cold glacier and this type of glacier is less sensitive to climate change, than temperate glaciers.The natural ice palace and its small and large wonders will remain with us for quite a while.

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The age of the Hintertux Glacier

Now we know that the Hintertux Glacier will not be a thing of the past for a long time. But since when does it exist? The ice in Hintertux dates from the Little Ice Age and is around 500 to 600 years old. But these are the layers of ice that are now further down towards the valley.

We remember that the upper part of the Hintertux Glacier moves very slowly. The base is frozen. Consequently, the base must be significantly older than the upper-level ice, which eventually advances to lower-lying mountainous regions. "The oldest scientifically dated ice in the Eastern Alps is 5800 years old," Mr. Erler informs us.

But how old is the ice in the Natural Ice Palace? How old are the lowest layers in the 52 meter deep research shaft? They might even be older. Another record? Perhaps. But currently we have to be patient for a corresponding answer. "The dating is still open," explains Roman Erler with certainty. Future results from the researchers remain to be seen. It remains exciting.