Jonastal, situated in the Ilm-Kreis district in Germany between Crawinkel and Arnstadt and near to the town of Ohrdruf, was a scene of military construction under the National Socialist regime during the last years of the Second World War. Thousands of prisoners from the Buchenwald concentration camp under the command of SS General Hans Kammler were forced to dig 25 tunnels into the surrounding mountain and the whole operation was performed under the strictest secrecy. The site was not completed and construction was abandoned before the end of the war.

Ohrdruf was a German forced labour and concentration camp located near Ohrdruf, south of Gotha, in Thuringia, Germany. It was part of the Buchenwald concentration camp network.