Water pipeline (outside)

The Carolingian long-distance water pipeline had a length of 6.5 km and originally ran around 0.5 – 1.5 m below the surface. It carried water from the “Orbel” spring near Heidesheim with an average gradient of 0.7-0.8 % (difference in altitude a good 37 metres) to Charlemagne’s Palatinate. Here there were various branches for distributing the water.

The construction, made of local limestone rubble, arched over a 42 cm wide pipe channel, which was plastered with a waterproof mortar. It is easily recognisable due to its red colour, which comes from the brick dust mixed in. The Romans already used this special mortar (opus signinum). As the entire construction follows Roman principles, it was long thought to be an ancient building. It was not until 1996 that it was scientifically proven that it was built at the end of the 8th century, i.e. during the first construction phase of the imperial palace.

It is unclear why this immense effort was made, as there was sufficient groundwater in the Imperial Palace area. Charlemagne’s architects were probably inspired by the ancient long-distance water pipes in Cologne, Trier or Mainz. As hardly any lime deposits have been detected in the channel, the pipeline appears to have only been used for a short time. Nevertheless, it is a unique technical monument that documents the skill and knowledge of Charlemagne’s master builders.

In the Kaiserpfalz Archaeological Zone, you can see the end of the long-distance water pipeline in its original position: Follow Mainzer Straße eastwards until you reach François-Lachenal-Platz. Walk past the museum and then turn right into the street “Im Saal” and after about 50 metres turn left into Karolingerstraße. Walk past the Saalkirche church and turn right towards the entrance to the “Heidesheimer Tor” monument area. There you will pass through a narrow passageway to the outside of the semi-circular building, where you can recognise the brick-lined, vaulted canal on the ground.