Travels in Geology: Austria's Salzkammergut: World heritage preserved in salt

by Terri Cook and Lon Abbott
Tuesday, July 18, 2017

Stunning Alpine scenery and historic attractions abound in Austria's salt district, the Salzkammergut. Credit: Lon Abbott and Terri Cook.

In Austria’s famous salt district, the Salzkammergut, the long arc of European history, so palpable to North American visitors wherever they travel through Europe, reaches especially far back. Nestled between stunning Alpine peaks and sparkling lakes are numerous salt mines, including those at Hallstatt, which are the oldest known on Earth. Artifacts from the mine date back 7,000 years to the Neolithic, or New Stone Age, period. Surrounding Salzburg, the region’s hub and picturesque home to Mozart, a compact driving loop wends past these mines and a series of other captivating sites that evoke the region’s rich heritage fortuitously preserved in salt.

Salzburg to Hallstatt

The graceful city of Salzburg, a World Heritage site and a major tourist destination, is an ideal launching pad for any tour of the Salzkammergut, which translates as “estate of the salt chamber.” Salzburg lies at the foot of the Northern Calcareous Alps, the first range of towering mountains one encounters heading south from northern Europe’s flat plains. It’s easy to immerse yourself in history wandering the old city’s streets, admiring the colorful baroque buildings lining the Salzach River and touring museums and palaces galore. Among Salzburg’s many highlights are the house where Mozart was born and lived until age 17, which features the mini-violin he played as a toddler, and the Hohensalzburg Castle, an imposing 900-year-old clifftop fortress. Further reinforced in the early 16th century, the castle sprawls across a limestone hilltop that rises above the old town. Accessible from the town center by a quick funicular ride or a bracing 30-minute uphill hike, the castle also serves as the spectacular backdrop for Mozart concerts each summer. Don’t miss the Stiegl Brewery as well, which has been in operation since 1492.

Salzburg is a great place to base yourself for a visit to the Salzkammergut. Credit: both: K. Cantner, AGI.

Once you’re ready to explore the Salzkammergut, the 73-kilometer drive from Salzburg to Hallstatt takes you through the heart of the beautiful Austrian Lake District. The first lake (“See” in German) you encounter, the Mondsee, lends its name to the Mondsee Group, a Neolithic culture that built stilt houses in the water between 3800 B.C. and 2800 B.C. The culture is known for its “Mondsee Copper” artifacts, a trove of which was discovered in 1864 when archaeologists excavated the remains of several stilt homes. While sifting through the mud, they discovered hundreds of stone axes, and arrowheads, 12 copper axes and six daggers along with charred hazelnuts and pieces of apple, organic material that would normally decay rapidly but that had fortuitously been preserved in the oxygen-poor mud.

Ötzi the Iceman, the famous mummy discovered in 1991 in the mountains along the Austrian-Italian border, carried a copper axe made by the talented Mondsee smiths. Alexander Binsteiner, who served as the chief geologist on the Ötzi project, hypothesized that the artifacts found at Mondsee were preserved when the village was inundated by a lake tsunami. He developed this hypothesis after a 2008 storm uprooted hundreds of trees, revealing a vast field of boulders left behind by a landslide that broke off the 150-meter-tall cliff that rises above the lake’s southern end. Binsteiner estimates the landslide dumped 50 million cubic meters of material into the lake, triggering a 5-meter-high tsunami. Although there are no interpretive sites there, you are treated to great views of the cliff while driving along the glistening lake.

Next, the route to Hallstatt passes the even bigger Wolfgangsee and the spa town of Bad Ischl before reaching the sparkling blue waters of 5.9-kilometer-long glacial Lake Hallstatt. The archetypal alpine village of Hallstatt huddles on a small river delta that constitutes one of the few flat spots in this fjord-like valley.

The Hallstatt Salt Works

The glistening Mondsee was once the home of a Neolithic culture best known for its stilt houses and copper artifacts. Credit: Aconcagua, CC BY-SA 3.0.

Hallstatt, a village of 859 people, is lined with classic wooden alpine houses in a picture-perfect lakeside setting. The primary attraction here is the World Heritage salt works, accessed by a funicular that whisks you up the hillside to the Hallstatt High Valley, where you can enjoy a meal on the terrace of a 13th-century tower built to guard the lucrative salt mine that affords sweeping views over the lake. Before your tour, be sure to walk out onto the skywalk, where you can gaze down onto the streets of Hallstatt hundreds of meters below.

Salzburg, the city of Mozart, flourished as the supply town for Austria's historic salt mines. Credit: David Iliff, CC-BY-SA 3.0.

The salt works entrance is a leisurely 15-minute walk up the valley. Interpretive signs and an audio tour inform you about the key historic sites en route. Chief among these is the site of a graveyard used by the area’s Celtic inhabitants between 800 B.C. and 400 B.C. More than 1,500 graves were excavated here in 1846, providing such a wealth of artifacts that Hallstatt became the type locale for the early Iron Age Hallstatt Culture (8th–6th century B.C.). Farther up"the trail stand a reconstructed Iron Age hut and a Bronze Age (13th–12th century B.C.) shed once used to cure salted pork.

The salt works tour has its share of kitsch, including a dazzling light show and amusement park-style miners' slides that allow visitors to glide between the mine levels. Fortunately, it isn’t hard to dig below the glitzy veneer to appreciate the mine’s impressive human history. Salt is such a good natural preservative that many ancient artifacts, including shoes, cloth and backpacks, have been found intact here. In 1734, miners even discovered a mummy, known as the “Man in Salt.” No archaeological analysis was performed on the mummy before it was reburied in the Hallstatt cemetery, but based on descriptions in the meticulous mine records, archaeologists suspect the miner lived during the Iron Age. The oldest artifact discovered here is a Neolithic pick made of stag horn, which indicates that these mines were operating by 5000 B.C. The highlight of the tour is a long wooden miner’s staircase, which evokes the daily lives of the miners who used it in 1344 B.C., according to dendrochronologic dating.

The Hallstatt salt is a diapir: salt deposited in an ancient sea rises up through denser, younger rock above. Credit: K. Cantner, AGI, after Schorn and Neubauer, Structural Geology, 2014.

The Hallstatt mine exploits a Permian salt diapir that constitutes some of this area’s oldest rock. The salt accumulated by evaporation in the newly opened, and hence shallow, Hallstatt-Meliata Ocean. This was one of several small ocean basins that formed in what is now Europe during the late Paleozoic and early Mesozoic, when the world’s landmasses were welded together to form the supercontinent Pangea. Pangea was shaped like a crescent moon that cradled the famous Tethys Sea. Subduction of Tethyian oceanic crust caused several slivers of continental crust to separate from Pangea, forming new “back-arc basins” (small oceans formed by rifting that is associated with nearby subduction) between the supercontinent and the newly rifted ribbon continents. The Hallstatt-Meliata Ocean was one such back-arc basin. As it continued to expand and deepen during the Triassic, evaporation ceased and reefs flourished; thick limestone deposits accumulated atop the salt. When the Hallstatt-Meliata Ocean closed in the Late Jurassic, the compression squeezed the low-density salt into a diapir that rose buoyantly, injecting itself into the Triassic limestones above. The Hallstatt salt diapir and its overlying limestone cap came to rest in their present position in the northern Austrian Alps when they were shoved northward as nappes (thrust sheets) during two separate collision events, one in the Cretaceous and one in the Eocene, that created the modern Alps.

The quaint village of Hallstatt has served as a salt-mining center for 7,000 years. Credit: Lon Abbott and Terri Cook.

Many artifacts recovered from the mine are displayed in the Hallstatt Museum, located in the heart of town, including wonderful specimens of the abundant ammonites found in the Triassic limestone surrounding the town. The Hallstatt Limestone is the world’s richest Triassic ammonite unit, yielding specimens of more than 500 ammonite species. For hundreds of years, Hallstatt miners have sold ammonites to tourists and museums, so the area’s fossils were well known to early geologists. Franz von Hauer’s exhaustive 1846 tome describing Hallstatt ammonites inspired renowned Austrian geologist Eduard Suess' detailed study of the area’s Mesozoic history. That work was instrumental in Suess being the first person to recognize the former existence of the Tethys Sea, which he named in 1893 after the sister of Oceanus, the Greek god of the ocean.

The Dachstein

A skeleton from one of the 1,500 Iron Age graves excavated near Hallstatt is on display on the path from the Hallstatt High Valley to the Salzwelten salt works. Credit: Lon Abbott and Terri Cook.

“Another local highlight is the plateau surrounding the 2,995-meter-high Dachstein, one of the Northern Alps' highest mountains. The massif is accessed by cable car from Obertraun, just 5 kilometers up the valley from Hallstatt. In addition to its tremendous views, the Dachstein is an outstanding place to examine the Triassic reef limestones that accumulated in the Paleo-Tethys Sea. One cable car whisks you up from the base station to the 1,350-meter-high plateau of Schön­bergalm, where you can tour two caves that are part of the extensive karst topography formed by dissolution of the highly soluble Tethyian limestone. Mammoth Cave (the Mammuthöhle) contains 70 kilometers of passageways, 1 kilometer of which you can visit during a 50-minute guided tour. The temperature in the nearby Dachstein Ice Cave (Eishöhle) remains below freezing year-round, allowing ice towers up to 9 meters tall to form inside. A separate 50-minute guided tour snakes around these sparkling towers.

After touring the caves, visitors can hop onto the upper gondola, which deposits you near the top of the 2,100-meter-tall Krippenstein, a peak that protrudes above the Dachstein Plateau. Here you can tiptoe out onto the Five-Fingers Lookout, a spectacular perch cantilevered over the abyss to gaze down at Hallstatt nearly 1,600 meters below. If you’re even bolder, you can hurl yourself off the peak strapped tandem with a paragliding instructor for a birds-eye view of the incredible mountain scenery before landing in the valley far below. Hiking trails of all lengths and difficulties abound, including several challenging “via ferrata” routes, which traverse the sheer face of the Krippenstein by means of wire ropes and iron ladders. A 30-minute walk to a kitschy iron shark sculpture is also worthwhile to see the “cow prints,” fossils of megalodont bivalves that thrived in the Tethys Sea.

Werfen and the Salzach River Valley

Some of the 500 species of ammonites found in the Salzkammergut are on display at the Hallstatt Museum. Credit: Lon Abbott and Terri Cook.

“Completing the loop back to Salzburg via Gosau and the Salzach River Valley provides still more breathtaking alpine scenery and fascinating history. More quintessential alpine hikes leave from Lake Gosau, which lies below an especially impressive, glacier-mantled face of the Dachstein. Beyond Gosau, the road winds through rolling, agricultural meadows, or alps, for which the range was named, before dropping into the scenic Salzach River Valley.

The rugged Dachstein massif rises above the Gosau Valley. Credit: Lon Abbott and Terri Cook.

Werfen, another classic alpine village (located 20 kilometers farther up the valley), is home to Hohenwerfen, the area’s most imposing castle, as well as the 42-kilometer-long Eisriesenwelt (“world of the ice giants”), the world’s largest ice cave. It takes at least three hours to tour the cave, starting with a winding drive or bus ride to the ticket window. From there, a gentle, 20-minute walk leads to a cable car that climbs to 1,576 meters elevation. This is followed by another stroll with grand vistas down to the Salzach Valley far below, up to the cave entrance. The 75-minute tour provides you with views of ice stalactites and ascends the edge of a giant ice cascade.

The Salzach Valley is dotted with a string of lovely alpine villages, each of which would make an ideal base for an extended tramping or biking holiday through the picturesque countryside. Walks range from a 10-minute stroll to lovely Gollinger Falls to rugged, multi-day alpine traverses.

The world's largest ice cave is in the Dachstein Limestone. Credit: Lon Abbott and Terri Cook.

Near the end of your loop in the town of Hallein, located just 29 kilometers from Salzburg, you can tour another ancient salt mine, complete with a ride on a historic miners' train. Mining at Hallstatt ceased for a time around 350 B.C. after a huge mudslide buried the mine. Although the facility was soon reopened at a slightly different location, Hallstatt’s heyday had passed, with the center of activity shifting to Hallein. Archaeological research has added yet more detail to our knowledge of the Hallstatt Celtic culture, with one of the most important finds from this mine being preserved human feces that allowed archaeologists to study the food trade among Iron Age cultures.

The imposing 16th-century Hohenwerfen Castle guards the rugged Salzach Valley near the classic alpine village of Werfen. Credit: Lon Abbott and Terri Cook.

For a dose of more recent history, consider taking another cable car ride up the 1,853-meter-tall Untersberg, located on the German-Austrian border, which offers panoramic vistas down to Salzburg on the east and, to the west, across the German Alps that surround Berchtesgaden, the location of the Berghof, Hitler’s vacation home and most-used World War II headquarters. You’ll soon be back in Salzburg, where your tour began, with a deeper sense of the long human and geological history that salt has catalyzed and helped to preserve in this spectacular corner of Europe.

© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.