There’s quite a bit about it. Clearly it’s a dam of some significance to the area:
en.wikipedia.org
www.oberharz.de
And the Harz in general. The region has a quasi mystical significance for the Germans, along with the local witches:
Verbringen Sie Ihren Urlaub im Oberharz: Hier finden Sie, was Sie für den Harzurlaub brauchen: ✓ Unterkünfte ✓ Urlaubsangebote ✓ Infos & Tipps
www.oberharz.de
If you fancy going back and seeing more, there’s plenty of stuff for motorcyclists and non-motorcyclists on the internet.