The Earthroom forms the scenography for the research project Archaeology of a city mine. Various soils from the Stuttgart 21 construction site were collected, dried, crushed and processed into plaster. For this process, we used our specially developed petrification technology, with which we process mineral materials as an alternative to conventional concrete. Visitors to the Archaeology of a city mine exhibition are invited to "go underground" through the earth room and view the finds collected from the Stuttgart 21 construction site in a new context. The earth is the medium that envelops the finds at the site and plays an important role in archaeology in determining the affiliation and origin of a find. This work therefore not only examines the possibility of reusing earth as a building material, but also uses its metaphorical meaning as a formal means.