1,700-year-old Roman fort discovered in Germany was built to keep out barbarians

Archaeologists have unearthed the ruins of a Roman fortress in Germany that once protected against barbarian intruders.

For more than a century, historians have suspected that a defense structure known as a castrum was lurking beneath a cobblestone street in Aachen, a city in western Germany. However, it wasn't until recent excavations ahead of a construction project that archaeologists finally saw the remains of the 1,700-year-old fortification. They immediately knew it was a Roman construction, according to a translated statement.

"The way the wall was built left no doubt it had to be of Roman origin," Donata Kyritz, an archaeologist and owner of sk ArcheoConsult, the firm that led the excavation, told Live Science in an email. "The concrete-like mortar and the choice of rock was typical for the Roman period. Also, the dimensions and the way the foundation was built differed from the technique used in medieval times."

The wall itself dates to around the third century and the segment that was unearthed stretches about 23 feet (7 meters) long and 35 inches (90 centimeters) wide. The full length of the wall is unknown, according to the statement.

Archaeologists think the wall may have been constructed in a circle protecting the city, the Miami Herald reported.

Related: Cult temples and sacrificial pit unearthed at ancient Roman camp in Germany

The wall also may have included a series of gates.