Wikipedia
Sieberstollen
The Sieberstollen is an adit (German: Wasserlösungsstollen) for water drainage in Sankt Andreasberg, in the Harz mountains. It was created during mining in the Upper Harz and named after the river Sieber into which it discharges its water. The opening position is in the Sieber Valley.
The first 11.7 km of the 13.1 km adit forms part of the Upper Harz Water Regale and has been declared UNESCO World Heritage Site in 2010.