Mining needed power, and in the Upper Harz the power came from rain. The silver, lead and copper mines around Clausthal and Zellerfeld went deeper over the centuries, and the water wheels that pumped and hoisted needed a steady supply high on a plateau with no big rivers. So miners, over about seven hundred years, built a network of reservoirs, ditches and tunnels that gathered every drop of rain and snowmelt and channelled it to the wheels. Many of the ponds and ditches were made between the sixteenth and nineteenth centuries, and a large part still holds water, which is why the system is on the UNESCO list.
What you see on the ground is quieter than the idea. A dam with a grassy crest, a pond with spruce on its banks, a narrow ditch tracing the contour of a hillside with a path alongside. The ponds look like natural lakes, and many are used for swimming or fishing now. The ditches are easy to miss unless you know to look for a thin line of water winding through the forest. The Oderteich, a big dam from the early eighteenth century, is the best known, and the Dammgraben and Sperberhaier Damm are among the ditches that walkers follow.
Clausthal-Zellerfeld, a town of about 15,000 people only a kilometre away, was the mining capital, and has a good mining museum, a technical university that grew from the old mining academy, and one of the largest wooden churches in Germany, the Marktkirche zum Heiligen Geist. It is a practical stop for fuel, bakeries and a bed. The old tradition shows in the greeting Glück auf, which locals still use.
The riding is classic Harz. Roads climb over the plateau through spruce forest, with gentle curves, some tighter bends on the descents to Goslar and Osterode, and the occasional view down onto the flatlands. Many of the spruces have died in recent dry years, and large cleared patches show where bark beetle damage has opened the landscape. Weather matters: fog and drizzle are common, snow can arrive early and linger on the high ground, and winter closes some minor roads. Late May and September are generally the best months. Try a Harzer cheese if you dare, or a plate of Schmalzbrot with a coffee in town.