The Thüringisch-Vogtländisches Schiefergebirge (Thuringian Slate Mountains, Vogtland Slate Mountains) stretch from the Thuringian Forest to the Ore Mountains. In English the term Thuringian Highland is common. It is a flat-walled low mountain range rump area approximately 300 m to 500 m asl. It extends about 75 km in an east-west direction and 50 km in a north-south direction. The most important towns are Saalfeld and Plauen. Particularly characteristic landscape features are diabase knolls (such as the Pöhlde or the Hübel) with their forest scoops. They consist of volcanic rocks, diabases, which are harder than the surrounding rock and therefore weather more slowly. This gives rise to the typical hilltops.
Although this area has a similar structure to the Harz Mountains, it lacks the sharp boundary of faults. Almost all around, the area has gradual transitions to its surroundings. The rocks that occur are rocks of the Palaeozoic era, i.e. from the Ordovician, Silurian, Devonian and Lower Carboniferous periods. The most important are clay slate, alum slate, siliceous slate, limestone, sandstone, greywacke, diabase, spilite and volcanic debris. Accordingly, there are quarries where the hard rocks are quarried for road construction, as well as mines, especially for alum and slate. As the name suggests, slate is the predominant rock.
Limestone subject to karstification, and thus cave formation, exists only in individual, small-scale areas. As a result, the number of caves is naturally quite small. So far, only one show cave has been opened in the entire area. This is the Syrauer Drachenhöhle (Syrau Dragon Cave). During the construction of the ICE line through the Thuringian Slate Mountains from Erfurt to Coburg, a spectacular dripstone cave was discovered. Unfortunately, tunnel construction led to its partial destruction and the closure of the entrance. What remains is an illustrated book with extraordinary photographs.