Antique counterpart to barbed wire

The structure made of sharpened wooden posts was discovered in surprisingly good condition and was subsequently recovered. © Goethe University Frankfurt / Frederic Auth

Previously, the “pila fossata” were only known from written records. But now, for the first time, archaeologists have been able to recover, examine and preserve the remains of these Roman obstacles to approach. The constructions made of sharpened wooden posts were discovered at a site in Rhineland-Palatinate. The research team reports that the spiky defense technology there was apparently intended to prevent Germanic tribes from reaching the ramparts of a Roman military camp around 2,000 years ago.

The remains of two Roman military camps from the first century AD lie dormant in the ground near Bad Ems: This has been uncovered by an excavation project lasting several years since 2017. The evaluations of the finds, completed in 2023, show that the facilities served an ancient mining project: The findings match a traditional text by the Roman historian Tacitus, according to which there was a search for silver veins in the region. However, it was apparently unsuccessful, which is why the systems were probably only used for a few years. First, the archaeologists led by the Goethe University Frankfurt aM came across traces of the larger of the two fortified camps. Its dimensions reflect the enormous effort involved in the ancient mining project: the facility covered around eight hectares, was equipped with an earth wall and wooden towers and offered space for 3,000 men.

A spiky structure appears

However, the special find that the team is now highlighting comes from the second facility, which was later discovered about two kilometers away from the first. According to the excavation results, the construction on the “Blöskopf” was a small fort that apparently served to protect the Roman mining area. The discovery of a coin minted in 43 AD also referred to the middle of the first century AD. The special discovery involved the remains of a special element of the fortification of the complex: “In the inner pointed ditch of the small fort we have sharpened wooden stakes found in a defense system. What is remarkable is that the finds have been preserved in their original functional construction context,” reports Markus Scholz from the Goethe University Frankfurt.

After the on-site examination, the total of 23 wooden elements were recovered and taken to the specialized laboratories of the Leibniz Center for Archeology (LEIZA) in Mainz for more detailed examination and preservation. The research team has now introduced it in a public presentation and explained its significance. It was therefore a Roman defense technique that was called “pila fossata”. “These obstacles to approach were described by ancient authors such as Caesar, but this was the first time that archaeological evidence was found in the entire Roman Empire,” says Scholz.

The skewers preserved on the LEIZA at the presentation. © LEIZA / Sabine Steidl

Archaeologically tangible for the first time

The investigations revealed that these were arrangements of approximately 55 centimeters long skewers made of hard oak wood. In order to fortify it, it was dug into the bottom of the tapering ditch that once surrounded the small fort on the Blöskop. The archaeologists found them in this condition. “We owe these unusually well-preserved archaeological finds primarily to the oxygen-poor wet soil, which was covered by dense layers of sediment,” says Markus Wittköpper, an expert in wet wood preservation at LEIZA. This slowed down the decomposition of the wood material.

Visualization of the function of the pila fossata. © Goethe University Frankfurt / Karlheinz Engemann

The spiky structure apparently served to prevent attackers from reaching and scaling the fort's palisaded wall. The pila fossata at the bottom of the trench also had a trap function: anyone who slipped into the tips could sustain life-threatening injuries. Having tangible remains of this ancient defense technology in front of you is something very special, explain the archaeologists. Alexandra Busch from LEIZA says: “These seemingly inconspicuous wooden posts from the military camp near Bad Ems are a small sensation for archeology, which I am particularly pleased about as a specialist in the Roman military.”

Source: Leibniz Center for Archeology

The results of the excavations were summarized in a publication: Dr. Peter Henrich and Prof. Dr. Markus Scholz (ed.): The early imperial military installations near Bad Ems in the context of Roman miningReports on archeology on the Middle Rhine and Moselle, Vol. 23, 2024.

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