The Fossa Carolina
The Fossa Carolina is a cultural monument of European-wide importance. Located to the north of the village of Graben the “Graben” or dyke lends the village its name. In 793 Charlemagne wanted to connect the Danube and the Rhine rivers by a navigable channel between the Altmuehl and Rezat rivers. The dyke’s location was meticulously planned. Here both river systems are just 1800 metres apart and the highest point of the European watershed is only 12 meters above the level of the river Altmuehl.
Whether the Carolingian hydraulic engineers completely succeeded in their task is disputed. Historical sources tell us that there were long periods of heavy rains and unfavourable geological conditions that prevented the system’s completion but if it was unfinished it was probably due to political reasons. However, it is relatively certain that a connection between both river systems existed and was utilized, at least for a short while.
Visitors can enjoy a leisurely walk around the tree-lined embankment of the dyke. The fountain at the European Watershed on the dyke’s northern edge is a popular destination. The water from the fountain is channelled into two rivulets: one of them flows into the Fossa Carolina and then in the Altmuehl which flows into the Danube; the other one flows into the Rezat, then the Main and finally into the Rhine.
An exhibition on the Fossa Carolina is located in a former barn in the village and is well worth a visit. It was installed for the 1200 year anniversary of the Fossa Carolina which occurred in 1993.
The earliest written reference to the Fossa Carolina can be found in the Annals of Lorsch. This account apparently goes back to the imperial archives, which were officially recorded. They describe Charles’ journey to the Fossa between the Altmuehl and Rezat rivers and further on to the river Main to Wuerzburg. An extended visit by the court to the building site is explicitly mentioned.
The area between Weissenburg and Eichstaett played an important role in Charles’ imperial politics. After the downfall of the Bavarian duke Tassilo III in 788 Bavaria was annexed and became part of Franconia; a regional plan was established and the building of new villages began.
Well-fortified settlements were built forming a half-circle from the Franconian royal court in Weissenburg to Eichstaett (which in those times was the Franconian bishop’s seat) to the former Bavarian duke court of Tassilo in Neuburg on the Danube. This was done to ensure the union between Bavaria and the Franconian state. The Fossa Carolina was probably built for the same reason. A continuous waterway between the heartland of the empire and the Danube would have strengthened the attachment of Bavaria to Franconia; but the Fossa Carolina could also have been intended as a transport link for trade.
For centuries there have been studies and articles on the Fossa Carolina. Two conflicting theories have emerged.
The first is that the Franconian engineers wanted to connect the Altmuehl and Rezat rivers with a channel at the same level as the Altmuehl so that boats could pass through unhindered.
The second theory goes that, instead of one continuous canal, ponds may have been built in an ascending chain. The boats would have had to be pulled over several banks. This difficulty would likely have been solved with winches and slides as canal locks had not yet been invented. Because this would have involved a lot less earth moving, nowadays, it seems that this is the most plausible explanation.
