Archaeologists discover a hidden treasure in a river dating back 2,000 years

A team working along the Sava River in northeastern Bosnia and Herzegovina lifted a cluster of ancient iron bars after just two days of diving.

The cache points to the late Iron Age, when La Tène communities overlapped with the advance of Rome, roughly the 1st or 2nd century BC.

After the fieldwork wrapped, one diver’s name surfaced in reports. Krunoslav Zubčić, a senior conservator archaeologist with the Department for Underwater Archaeology at the Croatian Conservation Institute, helped lead the professional recovery.

Iron ingots in the Sava river

The bars are bipyramidal ingots, a form of semi processed iron shaped like two joined pyramids.

Metalworkers once used them as movable stock that could be reheated, welded, and forged into tools, blades, or fittings.

These ingots act like a time tag. Their shapes and corners follow patterns that specialists use to sort them by workshop traditions and date.

“In this case, we are talking about a large quantity, nearly two hundred pieces,” emphasized Zupcic.

Researchers have cataloged many single finds, but large groups are rare and important for economic history.

A 2017 study on late Hallstatt and early La Tène iron reported that bipyramidal semi products cluster in Central Europe and that around 500 examples are known.

That context helps frame what lay under the Sava. A cache nearing two hundred pieces in one place changes the scale and the questions scholars can ask.

How the bars were made

The team will probe how the bars were made and where the ore came from.

One approach compares trace elements and isotopic fingerprints against known ores and slags to narrow down potential mining districts.

Dating the metal matters too. Direct radiocarbon dating of the carbon trapped in ancient iron has proven feasible when careful sampling avoids contamination.

Analyses like these will not just stamp a date range. They can show whether the Sava cargo carried iron from a single source or a mix assembled along a trade route.

Sava River and ancient iron trade

The shape and size of these ingots match items used as standardized trade stock.

If their chemistry links to ore from the eastern Alps or Pannonian Basin, that would tie Bosnian Posavina into a wider network of exchange that reached north and west across the rivers.

“We will establish contact with those museums, that is, experts from that area,” stated Jezercic, director of the Museum of the Franciscan Monastery: Tolisa Vrata Bosne, flagging the need for cross-border expertise and funding. 

The Sava River iron ingot find also shows the careful method behind underwater archaeology.

Teams map the bottom, fix reference points, and use photogrammetry to stitch overlapping photos into a 3D model that preserves the exact layout.

Each object then moves into distilled water so salts leach out slowly. That step protects the iron from crumbling during conservation.

What the shapes can tell us

Bipyramidal forms vary in length, angle, and end treatment. Those small differences can mark workshops or regions when compared across many finds, something only possible with sizeable groups.

Scholars will scan these bars for hammer marks and weld lines that record the archaeometallurgy of their makers. Patterns of slag inclusions, porosity, and steel zones also reveal choices about heat and working.

Finds like this sharpen the picture of what people in the Balkans made, traded, and valued at the end of the Iron Age.

If the bars traveled on river craft, the Sava and its tributaries were not just boundaries, they were corridors.

Trade routes rarely run in straight lines. Ports, markets, and river crossings create stepping stones, and ingot caches mark those steps.

People behind the discovery

The story began with a local history enthusiast who noticed something odd in the murky water. That tip brought professionals who documented the site and moved the pieces safely into care.

Small museums often hold the keys to big questions. Teams that mix local knowledge with regional labs can pull together answers that no single group can reach on its own.

Provenance tests may point to one or several ore districts. If the chemistry splits into clusters, that would hint at a cargo assembled from different suppliers for a single shipment.

If dating and typology converge on the 1st or 2nd century BC, the find will slot into the moment when Rome’s frontier pressed east. That timing would help trace how Roman and Celtic economies knitted together.

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