They found a staircase, rare private altar and massive foundations of a late antique basilica.
Archaeologists were working alongside building crews when the find was made.
It was during construction of the LVR-Jewish Museum in Cologne, Germany.
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The site dates to the first century of Roman occupation with the oldest structure uncovered a part of a stone staircase.
Only the midsection survived, as reported by What’s The Jam.
It once led from the praetorium toward the River Rhine, though archaeologists have not yet determined exactly where the stairs began or ended.
The staircase was likely necessary because the natural slope of the terrain required stepped access between the palace complex and the riverbank.
A later Roman expansion of the praetorium filled in parts of the stairs to make room for additional buildings, unintentionally preserving this portion.
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Roman staircases are rarely found intact.
Excavators also discovered a second-century private household altar, or lararium, within the praetorium.
A lararium is typically built as a niche in a wall where offerings of food were made to the Lares, the household’s patron gods.
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The niche was carefully constructed with molding that distinguished it from the rest of the wall and allowed it to be closed.
It would have housed small figurines.
Archaeologists identified nail holes where iron nails once held garlands or ribbons as decoration, and traces of paint remain visible on the surrounding stucco.
The most recent discovery dated from the fourth century was foundations of an apse of a multi-aisled basilica.
Before excavation, the structure had only been perceptible as a shallow depression in the ground.
When the foundations were exposed, archaeologists realised the building was not made of typical Roman cast concrete.
Instead, it consisted of 13-foot-thick layers of volcanic rock, basalt and limestone, bonded with a strong mortar composed of crushed ceramic and gravel.
Its bulk and strength had allowed it to remain intact for nearly 2,000 years.
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