The Marienglashöhle cave near Friedrichroda is an impressive legacy of mining in Thuringia. Construction of the entrance tunnel began in 1775 in the hope of finding copper there. In 1778, instead of the hoped-for copper slate, an extensive gypsum deposit was found; the deposits were exploited in underground mining until 1903. In 1784, a gypsum crystal grotto, the only natural cavity in the mine, was discovered in the mine. Today it is considered one of the most beautiful and largest gypsum crystal grottoes in the whole of Europe. Over a diameter of almost ten meters, millions of years of geological formation processes have formed colorless, transparent gypsum crystals up to 90 cm long. The gypsum crystals were used to decorate images of the Virgin Mary. It was at this time that the current name Marienglas came into use. In 1848, the mining of the crystals was banned, thus preserving a unique natural monument.

During guided tours through the 110-metre-long entrance tunnel, geological windows on the right and left of the walls provide a view of the different layers of rock. You can also marvel at the tools and pit cages used to mine and extract the gypsum crystal. The attraction of every visit is the unique crystal grotto. A footbridge around 70 meters long bridges the cave lake with its charming water reflections and leads to the western part of the show cave. At the end of the impressive tour, you can buy souvenirs for your loved ones at home in the mineral store. A treat for music lovers are the »Underground« concerts in the winter months. For these special events with unique acoustics, the cave is illuminated with several hundred candles.