Archaeologists excavate the apse of the Praetorium’s basilica. Credit: City of Cologne/Roman-Germanic Museum, Michael Wiehen.
The jackhammers are a common occurrence in modern Cologne. The city’s rich history goes back to the Roman times, and finding archaeological remains isn’t new. This time, the discovery came from the site of the future MiQua (the Jewish Archaeological Museum).
This museum isn’t your average construction. Archaeologists knew there were some ancient structures on site, so the plan was to build the museum to sit literally on top of history. But as the trenches went deeper this month, they came across way more than they were expecting.
Right beneath MiQua, close to Cologne’s City Hall, archaeologists have uncovered a massive 4th-century foundation, a 1st-century staircase that once climbed from the banks of the Rhine, and — most stunningly — a 2nd-century private altar. This altar, known as a lararium, is the first of its kind ever found north of the Alps. It’s something you’d expect to find in Rome or Pompeii, not in Germany.
Scratching the Surface
Cologne was once Colonia Claudia Ara Agrippinensium, a powerhouse of the Roman Empire. The governor lived here in a massive palace called the Praetorium. We’ve known about the palace for decades, but apparently, it still has a lot of secrets; some of which are really big.
Modern archaeology usually yields fragments: a broken pot, a rusted coin, the stump of a wall. We rarely get to see spectacular structures or secret passages. That’s why the discovery of a nearly 2,000-year-old staircase is so remarkable.
The Roman staircase dating back to the first century. Credit: City of Cologne/Roman-Germanic Museum, Franziska Bartz.
Now, the area is flat, leveled by centuries of urban development, covered by a modern plaza. Back in the 1st century, when the stone steps were built, this was a dramatic slope leading down to the Rhine river. To manage this, the architects of the Praetorium built a series of terraces. The staircase was a connective structure that linked the high grand halls of the governor’s palace with the bustling, lower levels.
But medieval builders loved using Roman stairs. In the Middle Ages, if you wanted to build a basement or a wall, a Roman staircase was basically a free Lego set of pre-cut blocks. Most stairs in the Roman Northern Provinces were “quarried” out of existence centuries ago.
This one survived, apparently, because of how much the Romans built around it.
×
Thank you! One more thing…
Please check your inbox and confirm your subscription.
Early in the palace’s history, the governors decided they needed more space. Because of the topography, this meant filling in the lower levels with massive amounts of earth and rubble to create a flat platform for expansion. They essentially mothballed their own architecture. By burying the stairs under meters of fill, they protected them from the medieval looters who would come 1,000 years later.
The Altar at the End of the Stairs
If the staircase is unexpected, the lararium is outright shocking. Not because these altars are rare in general, but because they’re unheard of in this part of the continent.
In every Roman home, from the grimiest apartment in Rome to the grandest villa in Tuscany, there were the Lares. These were the household gods — the spirits of the ancestors and the protectors of the hearth. A lararium was their home. It was a small shrine where the family would offer bits of food, pour a little wine, or light a lamp to ensure the house didn’t burn down and the children stayed healthy.
This lararium is the crown jewel of the dig. Because while these are common in the ash-preserved streets of Pompeii or Herculaneum, they are virtually unheard of in the northwestern provinces of the Empire. Usually, centuries of rebuilding and stone-robbing leave nothing but dust.
This is a window into the psyche of a Roman governor. Imagine a high-ranking official, thousands of miles from the Mediterranean sun, standing in a cold room in Cologne. He isn’t at a public temple praying to Jupiter for a military victory. He is at his private altar, performing the same small, intimate rituals his grandfather did back in Italy. It shows that even at the edge of the empire, the “Roman-ness” of daily life was fiercely preserved.
Beyond the Stones
The team also re-excavated a massive 4th-century basilica foundation, measuring an incredible four meters (13 feet) thick.
Unlike standard Roman concrete (opus caementicium), this structure was built with a specialized “super-mortar” known as cocciopesto. By mixing crushed ceramics and gravel into the lime mortar, Roman engineers created a composite material so durable it resisted nearly two millennia of decay. The foundation consisted of regular layers of volcanic tuff, basalt, and limestone — a testament to the high-stakes engineering required to keep a massive imperial building from sliding into the Rhine.
The MiQua museum plans to integrate these structures in situ, allowing future visitors to walk through the same underground passages where Roman elite once made offerings to their household spirits.
Although, who knows what else they’ll find next?