The city beneath the city: part 2

In part 1 we looked at the sewer system of Paris but now were going to go way back in time and a bit further east to Cologne.

Part 2: Cologne, the Roman Colonia Claudia Ara Agrippinensium (CCAC).

Travelling over to Cologne, and way back in time, I found myself, for the second time, down in a sewer. This sewer is without poo these days but in its day it was the main sewer of Cologne.


The cloaca maxima (main sewer) of CCAA lies about 10m under the modern street, Grose Budengasse and is accessible for about 150m.



The Romans are rightly known for their skills in engineering, urban planning and hydraulics. Cologne attained the status of imperial capital of its province, Lower Germany (Germania Inferioris) by the mid-third century and was well provided with all the infrastructure and facilities you’d expect. Aqueducts brought water to the city from sources in the foothills of the Eifel mountains, about 90km away. Water conduits and public fountains formed one half of the cycle of civic water management. The sewer system formed the other half.

The sewer is constructed from well-cut blocks of tufa (a porous limestone) together with some bits and bobs of reused material.


The cutting of the stone for this construction would have been carried out by masons, probably being paid according to the number of stones cut. I spotted what looks like a mason’s mark on one of the stones, used to identify the work of a specific mason.


A small part of the sewer system has been taken up and reconstructed at ground level, nearby. This makes it easy to see the voussoirs  (the wedge-shaped stones) that form the arched ceiling.


Waste from public and private toilets washed into the sewer, which was accessed via vertical shafts. This one has been reconstructed from the original stones


The tunnels must have been easily accessible for over a millennium because they were used as cellars during the middle ages and then as air raid shelters during the Second World War. Then they seem to have been misplaced but were rediscovered as the result of works to Cologne’s transport system.

If you want to visit the cloaca maxima, it’s accessed via the Praetorium exhibition on Kleine Budengasse.

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