Founded in 1990, and expanded in 2018, the nature park now covers and area of more than . It extends around the Rennsteig and comprises almost the entire Thuringian Forest and the Thuringian Highlands with Eisenach in northwest and Sonneberg in the south. The nature park protection includes the biosphere reservation, and a number of dams such as Tambach-Dietharz Dam, Schmalwasser Dam, Ohra Dam, Lütsche Dam and the Leibis-Lichte Dam.