Over several centuries here has been created labyrinth of passages. Here has been mined white sand for production of glass (initially - to disperse it in rooms) in 19th century. Total length of passages - 351 m. Earlier the passages have been longer, ceiling has collapsed in numerous places. Nowadays visitors can access only the newest part. There are stories about much larger systems of passages nearby. Passages were opened for tourists in 2001, one has to pay to enter the passages. Entrance has been reinforced.