Archaeologists have confirmed the presence of a long-lost Roman military camp deep in eastern Germany. The 18-hectare site, found near the town of Hachelbich in Thuringia, would have sheltered a Roman legion of up to 5000 troops. Its location in a broad valley with few impediments suggests it was a stopover on the way to invade territory further east.

“People have been searching for evidence of the Romans in this part of Germany for 200 years,” says team leader Mario Kuessner, an archaeologist working for the state of Thuringia. “It took a long time before we realized what we had, and we wanted to be sure.”

After a stinging defeat in 9 C.E., Rome largely abandoned hope of conquering the fractious German tribes north of the Rhine River. Yet written sources suggest that the Romans occasionally campaigned in Germany, probably to punish German tribes for raids on Roman territory. Until recently, the reports have been largely dismissed as braggadocio. The Hachelbich site, along with a battlefield near Hannover uncovered in 2008, show that the reports had more than a kernel of truth to them—and that the Romans were willing to cross their frontier when it suited their political or military needs.

The encampment was discovered in 2010, during routine excavations as part of a road-building project. In the years since, Kuessner and his collaborators have excavated more than 2 hectares and used geomagnetic surveys to analyze disturbances in the soil over an additional 10 hectares to reveal the outlines of the camp.

A rough rectangle with round corners, the camp is standard Roman military issue. No matter where they were, legions on the move set up a minifortress in the wilderness at the end of each day’s march. At Hachelbich, the meter-deep trenches dug around the camp were the easiest feature to spot in the soil. Two perimeter trenches have been found, each more than 400 meters long.

On the camp’s northern edge, the soldiers built a gate protected by another trench that projected out past the perimeter. “It’s typically Roman—no Germans did that sort of thing,” Kuessner says. The trenches were part of a simple, but effective makeshift perimeter defense: A low wall of dirt was thrown up behind the trench, then topped with tall stakes, to create a defensive barrier almost 3 meters wide and 3 meters high. Erosion wiped away the wall long ago, but it left discolorations in the soil where the trench was dug.

Additional evidence of an ancient encampment includes traces of eight makeshift bread ovens not far from the camp perimeter and a handful of artifacts, including four nails from the bottom of Roman boots, a piece of horse tackle, and part of a scabbard. The style of these artifacts—and a few radiocarbon dates—place the camp somewhere in the first 2 centuries C.E., too broad a range to be linked to a known specific event in Roman history.

Michael Meyer, an archaeologist at the Free University of Berlin, who was not part of the team but who attended a press conference about the discovery last week, says that any of the elements by themselves wouldn’t have been convincing, but together the find is compelling. “Now we have the first camp that’s clearly more than a day trip from the edge of the empire,” he says. “It’s no isolated frontier outpost, but something that clearly points to the Elbe River,” hundreds of kilometers deep in German territory.

The site’s exact whereabouts are being kept under wraps, to protect it from metal detector hobbyists who might loot or disturb it. When the fields of wheat and canola that cover it are harvested in the fall, excavations will continue. “The best would be if we could find coins or something with the legion number written on it,” Kuessner says. “That would help us pin down the date.”