Archaeologists uncover 300-metre Iron Age salt-mining complex

Archaeologists from the Natural History Museum in Vienna have discovered a large complex of Iron Age mining chambers in Hallstatt, Upper Austria, ORF reported. The chambers extend for about 300 metres and offer new insights into prehistoric salt production.

People were extracting salt in the high valley above Hallstatt as early as 7,300 years ago, according to tools found inside the mountain. From around 1200 BCE, salt mining reached almost industrial proportions, the museum said.

Landslides repeatedly ended individual mining phases, but miners resumed work after each event. “This was a very resilient community that was supplying salt again just a few years after these landslides,” excavation director Daniel Brandner of the museum’s Prehistoric Department told the Austria Press Agency.

Chambers arranged in parallel

Until now, researchers had known about prehistoric mining only where historic tunnels happened to intersect the older mining zones. Since 2022, they have therefore carried out exploratory drilling with a core-drilling machine operated by Salinen Austria.

The investigations have revealed an extensive complex of several parallel chambers. Some lie above or below one another, Brandner said. Researchers had not previously seen such a structure in Hallstatt.

The shape of the chambers shows that the prehistoric miners adapted closely to the geological conditions. Researchers have so far traced the complex over about 300 metres. The chambers are believed to be around 25 metres wide and 20 metres high.

Waste preserved by salt

The floors are covered by a layer of mining waste up to nine metres high. It includes burnt pinewood splinters, damaged tools, textiles and clothing fragments, as well as human excrement and food remains.

The salt in the mountain has preserved the finds exceptionally well, according to the museum. It conserved not only textiles but also DNA traces from food and human waste.

The discoveries provide the first detailed insight into a previously little-researched phase of Iron Age salt mining, the museum said. Researchers also noted similarities with finds from Dürrnberg near Hallein in Salzburg, where salt was also extracted from the sixth century BCE.

Historic tunnels undergoing repairs

Alongside the current excavations, a restoration project is under way in the salt mine. Archaeologists are working with Salinen Austria and Salzwelten to make older find locations accessible again. The federal government and the province of Upper Austria are funding the project.

Some tunnels that are several hundred years old are being secured and modernised. The aim is to re-examine former find sites with new methods and preserve the infrastructure for research in the long term.

Researchers are also presenting their work to the public at the “Archaeology on the Mountain” event in Hallstatt’s high valley. This year’s focus is the development of salt transport from prehistoric times to the present.