How a seventeenth-century drainage tunnel became a vital piece of world heritage

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: Deep beneath the Harz mountains, the Grünhirscher Stollen once served as a critical lifeline for silver mining. This massive water drainage adit, begun in 1691, eventually became part of a UNESCO World Heritage site. Its history reveals the immense engineering ingenuity required to keep early industrial mines from flooding.

The Grünhirscher Stollen, or Green Stag's Adit, was constructed in Sankt Andreasberg to manage water in the Upper Harz mining region. Work commenced in 1691, and for nearly two decades, miners relied exclusively on hammer and pick to carve the first 1.4 kilometers toward the Samson Pit. By 1729, the adit had expanded to connect with the Wennsglückt pit, coinciding with the peak production era for the local mining industry, where primary shafts like Sankt Andreas and König Ludwig reached depths of 400 meters.

As mining operations pushed deeper, the limitations of the Grünhirscher Stollen became apparent. Because the adit could no longer effectively drain the lower levels, construction on the Sieberstollen began in 1716. This new, lower-altitude drainage system eventually replaced the Grünhirscher Stollen in 1754. However, the older adit remained functional for industrial purposes, as its waters were redirected to power flatrod systems within the Samson and Wennsglückt pits. By the early 19th century, complex networks of drifts existed beneath the adit, with the 16th drift in the Samson Pit serving as a primary drainage route even before the Sieberstollen was completed.

Today, the legacy of this engineering feat persists in unexpected ways. In 1922, the Samson Pit became home to the Grüner Hirsch hydroelectric power station, situated 130 meters underground. This facility, one of two in the pit, generates electricity using water from the Oderteich. While the Grünhirscher Stollen now discharges its waters into the Sperrlutter, its historical significance is recognized globally. A 7.1-kilometer stretch of the total 10.2-kilometer adit is officially designated as part of the Upper Harz Water Regale, a UNESCO World Heritage site that preserves the remnants of this sophisticated water management network.

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