The most expensive mistake in ancient Roman history
Two thousand years ago, the Roman Army embarked on a far-flung hunt for silver. A new discovery reveals how close they came to finding an empire-altering fortune.
The passage is easy to miss. A paragraph-long anecdote in the Annals by the Roman historian Tacitus, it tells a story found nowhere else, about an unpopular legate forcing legionaries into a treacherous mine at the frontier of the empire. It takes place during the reign of Claudius (A.D. 41–54), a time of furious expansion when Rome sought to swallow up the borderlands and their resources. The location mentioned in the Tacitus passage is vague, described as “in the district of Mattium,” just outside of Roman-occupied Germania Superior. But the goal is clear: to find more of a metal that powered the realm.
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Silver trickled down from patricians, officers, and soldiers to the rest of the economy, in the form of coins and ingots and jewelry. Coins were not merely currency. Stamped with the profile of the emperor, each one served as a symbol of his power as it circulated across the land. The bulk of Rome’s mined silver had until then come from Hispania (modern-day Spain and Portugal), but prospectors had long sought other deposits across the dominion.
In Tactitus’s telling, the legionaries were “worn out” by the arduous, dirty, and dangerous task of mining, “of digging out water-courses and constructing underground workings which would have been difficult enough in the open,” let alone in the stifling darkness, broken only feebly by the glow of oil lamps. To voice their displeasure, the legionaries wrote a letter to the emperor, asking him to recognize the efforts of their unpopular commander, Curtius Rufus, with triumphal honors. Such an acknowledgment, they hoped, would permit Rufus to drop the largely fruitless effort. Eventually the search for silver was abandoned, and the army’s encampment destroyed.
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Tactitus’s story long intrigued classical scholars, who could find no evidence nor any other mention of such an undertaking. Some scholars dismissed it as a colorful but unverifiable aside. Alfred Hirt of the University of Liverpool, a specialist on Rome’s economy and mining operations, called it an example of so-called “mirabilia, which are these kind of wondrous stories that are being told just to regale readers.”
But a recent discovery that has electrified the archaeological world suggests that Tacitus was outlining a real episode. Rufus and his men indeed searched for silver, it seems, but decamped before hitting the mother lode. We now know there was enough silver in the region to have altered the course of the empire. But the enormity of their near miss would not become clear until millennia later, after a persistently curious German hunter put all the pieces together.
On a crisp evening in April 2016, a 72-year-old former paratrooper named Jürgen Eigenbrod was stalking boar in the hills around the historic spa town of Bad Ems, in Rhineland-Palatinate. He noticed an unusual pattern in a grain field: two parallel, yellowish strips cutting across a blanket of green. Few other passersby would have made anything of it. They were too wide to have been truck or tank tracks. Conspiracy theorists might have suggested an extraterrestrial origin. Eigenbrod knew better.
He had served with the blue helmets in Somalia and as a defense attaché in Tel Aviv, but since retiring from the German military in 2003, he had turned his attention to goings-on closer to home—if far distant in time. Eigenbrod had become fascinated with the archaeology and history of the Bad Ems environs and had even led a number of small-scale excavations of the Lahn Valley as a volunteer.
Amateur though he was, he recognized the crop marks as the sure sign of a human-made structure, keeping in mind a core tenet of archaeology: There are no straight lines in nature. Something beneath the ground had changed the density of the soil, causing the vegetation at the surface to mature at a different rate. But what?
To get a clearer view, he asked his old friend Hans-Joachim du Roi, a retired frigate captain and fellow history buff, to photograph the field from above with his drone. The aerial shot revealed that the parallel lines made a right-angle turn. The corner was rounded, like a playing card. Eigenbrod’s pulse quickened when he viewed the image. He had seen depictions of such a configuration before. There was only one thing it could be. The markings were the unmistakable traces of the defensive double trenches Roman troops commonly dug around military camps at the fringes of their empire.
Eigenbrod’s work had only just begun. “He had to convince the archaeologists of Rhineland-Palatinate in Koblenz to do some digging, and fortunately he did it like a pain in the ass,” said du Roi. “It was like the work of Sisyphus.” Worn down by Eigenbrod, the state’s archaeology department eventually agreed to conduct a geomagnetic survey of the surrounding area, on what is known as the Ehrlich plateau. Measuring infinitesimal variations in the Earth’s magnetic field, the survey revealed several other stretches of the double trench, confirming that it had marked the perimeter of a 19-acre Roman encampment, with fortifications of soil and wood.
Excavation of the Ehrlich camp began in 2017, led by archaeologist Thomas Maurer and supervised by Peter Henrich of Rhineland State Museum in Trier and Markus Scholz of Goethe University in Frankfurt. They initially believed the site to be from the time of Augustus (27 B.C.–A.D. 14), perhaps one of countless temporary marching camps Roman troops erected while on the move. Such camps have been found across Europe, often thanks to crop marks, but Frederic Auth, a doctoral student supervised by Scholz, put it bluntly: As archaeological finds go, they were “not so spectacular.”
However, Eigenbrod wondered whether Ehrlich might not instead have been a more noteworthy encampment. He was familiar with the enigmatic passage from Tacitus. The mention of the Mattiaci was an early clue, as they were a Germanic tribe who had settled near Bad Ems. Eigenbrod, who knew that the surrounding area had long been mined for silver, grew ever more convinced that the camp he had discovered was related to the mining operation Tacitus noted. Perhaps it was where the disgruntled legionaries had been stationed, he thought.
To the professional archaeologists, Eigenbrod’s hypothesis reflected the touching naivete of a dabbler. The archaeologists told the enthusiast this wasn’t how the discipline worked in real life. “It’s quite difficult to connect archaeology and historical literature,” Auth said, “and we tend to be very careful to not overinterpret that literature, because Tacitus has never seen Roman Germany.”
The hunter’s undiminished enthusiasm nourished the excavation—literally, as he kept the workers fed with homemade boar sausage. “Those sausages are quite the legend among the students,” Auth recalled. “I was giving a talk in Bad Ems, and my monetary compensation was actually more sausages from said boar.”
The dig unearthed, among other artifacts, a brass ring from a horse’s harness, iron nails, and slag, but precious little that might have allowed a precise date for the site. The archaeologists’ best clue was a heavily corroded bronze coin depicting a barely decipherable profile of Emperor Caligula, evidently minted in Rome in 37 or 38. Then, a coin of copper alloy from the subsequent Claudian period was discovered at the bottom of a former well. Coins could circulate for a long time, especially during Claudius’s reign, when few were minted, making it difficult to narrow down the time frame. But when combined with recovered sherds of pottery, including plates and jugs characteristic of the mid-first century, the finds led the team to date the Ehrlich camp to the 40s or early 50s. In other words, smack in the period Tacitus was writing about in the Annals.
Eigenbrod’s theory wasn’t yet vindicated. The time frame of Ehrlich may have aligned with Tacitus, but without evidence of a contemporaneous Roman silver mine, it could have merely been an intriguing coincidence. Finding such evidence would not be simple. The area around Bad Ems had been mined for various metals from biblical times up until the Second World War and is consequently riddled with pits, shafts, and tunnels, several of which are still accessible. “Some of these pits may be of Roman origin,” said Scholz, “but they were reshaped in medieval times or during the last few centuries.” In addition, the region had been heavily bombed in the war, making it difficult to distinguish craters from ancient mines. “We’re quite glad that Jürgen Eigenbrod was ex-military, so he can tell them apart,” said Auth.
Rather than attempt to find an undiscovered mine in a landscape full of holes, Eigenbrod insisted that the archaeologists shift their efforts to a nearby Roman site that had been known about for a long time: the remains of a small fortification on a barren hilltop less than a mile and a half away called Blöskopf (literally “bare head”). The site had been the subject of an 1897 study by retired Lt. Col. Otto Dahm, who, like Eigenbrod, had thought he’d found the elusive silver mine mentioned by Tacitus. Dahm concluded that Blöskopf had indeed been a smelting facility that he dated back to the end of the second century, far too late for Tacitus.
At Eigenbrod’s urging, Auth took another look at Blöskopf. He found that Dahm’s 19th-century publication was “pretty much full of errors,” showing few finds, and methodologically sloppy. With far more archaeological rigor, and technology unknown in Dahm’s day—including lidar to map the underground—Auth led a new excavation that unearthed a pair of coins from the time of Claudius or earlier, and none from the following reign, of his adopted son Nero.
The coins confirmed it: The large Ehrlich camp and the smaller Blöskopf outpost were in fact contemporaneous and most likely related. What’s more, the Blöskopf structure lay in an area now known to be a rich source of silver. Roman prospectors probably would have used several cues in the landscape to determine that Blöskopf could be a fruitful place to mine. The larger Ehrlich camp most likely served as the main Roman base in the area, which supplied the legionaries who worked the Blöskopf mine and manned the outpost. Based on this suspicion, Auth brought Eigenbrod to the tunnel that pierced through Blöskopf hill, along with Roman mining specialist Markus Helfert, who confirmed it was almost certainly of Roman origin. This was enough for the archaeologists to admit that Eigenbrod had been right all along. These were likely the places Tacitus was writing about.
Several weeks into the Blöskopf excavation, Auth and his team made a discovery that corroborated yet another passage from Roman history. In one pit, nearly six feet down, Auth and his team found what looked like the spiky backbone of a prehistoric monster. They cleared the reddish earth around it, revealing a series of sharpened wooden stakes jutting out at staggered angles and embedded in the bottom of a trench that once surrounded the outpost. Designed to thwart any would-be attackers, the obstacle appeared analogous to a defense Julius Caesar had described in his writings on the war in Gaul, a century before the Blöskopf fort was built: “Whoever entered within them were likely to impale themselves on very sharp stakes.” Caesar’s troops called the spikes cippi. Auth and his colleagues would call the version they found pila fossata, or “trench stakes.” Such dangerous devices are believed to have surrounded camps around the Roman world, but they have never been found in situ, before or since.
Just as thrilling as the discovery of the stakes was the miracle of their preservation. For two millennia, the dense, oxygen-poor soil had remained just moist enough to keep the stakes waterlogged and structurally stable. The pila fossata were extracted in 2019 and may have been conserved, according to Auth, just in time. Increasingly dry soil, he says, would have caused the wood to finally begin decaying, eventually destroying this precious testament to Roman ingenuity and ruthlessness. One can imagine the murderous spikes protecting the camp indefinitely, had the empire not abandoned its mining effort.
The likely confirmation of Tacitus’s account raised the question, How much silver had Rufus’s men missed? Auth’s study of Blöskopf revealed that the Romans got tantalizingly close to a source of silver-bearing ore that may have rivaled the richest mines of Hispania: the so-called Emser Gangzug, or Ems vein, which spans 10 miles from the north of Bad Ems to the Rhine River. It is estimated that more than 200 metric tons of silver were extracted in the modern era, before mining operations in Bad Ems were finally shuttered in the last weeks of World War II.
“If they had known about the silver, and if they had found the right spot,” Auth noted, the Romans “would have had the opportunity to exploit the Bad Ems silver for around 200 years until they abandoned their possessions on this side of the Rhine altogether.”
Roman forces had a secure hold on Germania Superior, but not on Blöskopf itself. They retreated west over the Rhine around 260, two centuries before the fall of the western empire. It is tempting to imagine how such a silver bonanza could have extended the reach or duration, or even hastened the decadence, of Rome—such counterfactuals are a perennial parlor game for historians, speculative as they must be. Had the legionaries succeeded in extracting all the silver that lay beneath their sandals, it “would not have sufficed to fund the whole Roman Empire” for centuries, “but it certainly would have made a difference,” said Auth. He cautioned that the silver-bearing ore was likely too deep for Roman technology of the time. The Roman authorities would have had no reason to linger in an area if they didn’t find a resource they could easily exploit. “If we don’t succeed effectively,” Scholz summarized Roman thinking, “then we drop it and go elsewhere.”
Jürgen Eigenbrod died of a heart attack in 2023, less than a week after a flurry of breathless press reports focused on the irony of the overlooked silver mother lode. He lived to bask, for a few short days, in the glory of his contributions to archaeology and history. Just as the Romans had 2,000 years before, he had gazed upon the land with an eye for the wealth that lay beneath. But unlike them, he had found what he’d been looking for.
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