During excavations on the railway network between Ebensfeld and Erfurt a karst cave was found in the Blessberg tunnel. The so called “Blessberg Cave” developed in lime stone of the Lower Muschelkalk, which formed the Herrenberg mountain. The investigations by the Thuringian Agency for Environment and Geology (TLUG), the mining agency of Thuringia, and the incorporated society of cave explorer in Thuringia revealed impressing objects (stalagmites, stalactites, sinter, excentriques, cave lake, cave creek), which were partly sampled; furthermore the extent of the cave was measured. The more than 1000 m long cave has no natural entrance and is not accessible anymore. Based on interdisciplinary studies on the sampled material information about the development and age of the cave will be obtained. Stalagmites represent an impressive and unique archive for climate and palaeoenvironmental changes. The growth of stalagmites can be linked to warm climate phases of past. In these warm stages, the growth of stalagmites depends on the precipitation and the water supply; thus palaeoenvironmental conditions are preserved. The aim is to decode the environmental conditions by decoding using high resolution techniques. In collaboration with the TLUG selected stalagmites and sinters will be dated by 230Th/U and analysed for their stable isotopic compositions.