The United Nations cultural organisation announced the news in a conference in Brasilia, Brazil, declaring that the 800-year-old system of canals, water-wheels, and underground water chambers would be Germany's latest World Heritage Site.
A committee of 21 experts decided unanimously to honour the water system in the state of Lower Saxony. Professor Reinhard Roseneck, responsible for environmental heritage in Lower Saxony said, "There's no comparable system anywhere in the world."
The water system is a pre-industrial energy supplier that provided power for the local silver, lead and copper mines until well into the 19th century. The earliest features date from the 12th century and were built by Cistercian monks.
Miners eventually dug 150 ponds, 500 kilometres of ditches and channels, and 160 kilometres of underground water-ways. Around 100 ponds have survived and many of the tunnels are accessible to visitors.
The most conspicuous feature is the Wasserregal, or water-shelf, built between the 16th and 19th centuries.
Lower Saxony culture minister Johanna Wanka called UNESCO's decision a "justified honour for this masterpiece of human creativity." She also thanked the local water authorities, whose financial support helped to maintain the famous water system.
Professor Roseneck, who also co-authored the 1,000-page application to UNESCO, said he hoped this decision would lift the Harz region out of its "Sleeping Beauty sleep," and stimulate the local tourist industry.