Elstermühlgraben

The Elstermühlgraben (litt.: Elster mill race or Elster mill ditch) is an approximately 4 km (2 mi) long, now partially underground mill canal in the city of Leipzig, Germany, in the Zentrum-West and Zentrum-Nordwest localities. It exists as an artificial tributary of the White Elster for more than 800 years.

Source: Wikipedia https://en.wikipedia.org/wiki/Elstermühlgraben