Since 1908, in addition to fossilized plants and animal remains, Pleistocene human remains have been found in the travertine quarries of the Ilm Valley, whose age is at least 120,000 years. They date back to the Eemian interglacial period, some finds could even be 200,000 years old. The Ehringsdorf prehistoric man, discovered in 1925, became world famous. The skeletal fragment was determined to be the largely complete skullcap of a prehistoric man. The large number of these finds from the Ehringsdorf quarries resulted in the designation of an archaeological protection zone in order to allow scientists to examine and recover valuable finds at any time. The regulation also had an impact on the operation of the quarry, so certain mining fields were reserved for research. The archaeological open-air site Weimar-Ehringsdorf was opened in 2009. In 1998, the Circle of Friends for the Establishment of an Open-Air Museum in the Weimar-Ehringsdorf Travertine Quarry had already achieved its designation as a protected landscape component.