The foundations of a Roman building that is probably the oldest library in Germany have been uncovered in central Cologne in archaeological excavations during the construction of a new parish building for the Protestant church.

The building dates back to 150-200 AD. It is at a minimum the earliest library in Germany, and perhaps also in the north-west Roman provinces.

The library is located in the middle of the ancient city, in the marketplace or forum. Based on its location and its being huge and built of very strong materials, archaeologists say it was a public library. It is estimated that the library held maybe 20,000 scrolls.

The walls were first brought to light in 2017. As Cologne was founded by the Romans in 50 AD under the name Colonia, the capital of the Roman province of Germania Inferior, archaeologists knew right away they were of Roman origins.

What perplexed them were the niches in the walls, measuring 80cm by 50 cm. Being too small to bear statues inside, archaeologists concluded they were kind of cupboards for scrolls. As Dirk Schmitz, the head of the Cologne archaeological monument authority said: “They are very particular to libraries – you can see the same ones in the library at Ephesus.”

“Perhaps there are a lot of Roman towns that have libraries, but they haven’t been excavated. If we had just found the foundations, we wouldn’t have known it was a library. It was because it had walls, with the niches, that we could tell,” he added.

As for the small annex to the building it was probably an alcove where a statue of the Roman goddess Minerva once stood, Schmitz said.

After the preservation, the walls and the three niches will be viewable by the public in the cellar of the Protestant church community centre, which is currently being built.