A „blue wonder of nature” can be observed almost every year at Hüttenrode. The open-cast mining hole left over from the limestone mining fills with the melting spring waters in spring. The water supersaturated with calcium then leads to a light blue colour.
Only with an increase in suspended matter and algae does the lake turn green.
The best chances of a seeing the beautiful blue colour is usually to be expected in the period from March to May.
Further information can be found here
here