The former slate gallery, where slate was mined from 1866 to 1927, has been used therapeutically for over 15 years. The slate gallery has been examined for its health-promoting effects in elaborate procedures, air reports and studies, and the often astonishing health improvements under the influence of the so-called 'Nordenau phenomenon' have since been scientifically substantiated by research results from a research group at Kyushu University in Fukuoka (Japan) and the participating Center for Holistic Medicine and Natural Healing Methods in Nordenau.The spring, which originates in the energy field of the gallery and is unique in Europe, carries high-quality so-called 'reduced water', which acts as a highly potent free radical scavenger for the general removal of metabolic waste products (so-called free radicals) from the body's cells, and the microclimate prevailing in the slate gallery is also unique. The temperature is a constant 8°C all year round and the air is almost saturated with water vapor (almost 100% humidity). The tunnel is therefore virtually free of dust particles, pathogens and allergenic pollen. In January 2011, Nordenau was awarded state recognition as a place with a healing cave.