In the Harz Mountains former mining has caused extreme heavy metal pollution in the river alluvials discharging from metallic ores or mining areas. Polymetallic soils developed since medieval times, when mining activities started in the 13th century. These metallic soils only allow fouthe growth of some-specialised metal-tolerant plant species and heavy metal plant communities, like Armerietum halleri. In the river valley of the Innerste near Hildesheim there are fine examples of typical vegetation on metal enriched river sediments. Some glacial relics belonging to the genus of Armeria, Silene, and Minuartia compound the characteristic species - pool of the endemic Armerietum halleri-community in Central Europe.