The Natural History Museum in Bad Sachsa sends visitors on a journey through 290 million years of natural development in the southern Harz Mountains. It starts with mount Ravensberg, which is the remain of a more than 100m high volcano. The visitor learns about the Ravensberg balls; stone balls that are filled with crystals and therefore sought after as collectors' items. Another exhibition shows the fossils of sea fish: cartilaginous fish, bony fish, ray-finned and lobe-fins fish. It also displays the beginning of today's land shape the gypsum karst and glacial as well as the world of dinosaurs. Pareiasaurus, protorosaurus and coelurosauravus were found here.