The "dripping down" of the brine over blackthorn twigs leads to the evaporation of water and the deposition of sparingly soluble salts on the thorn walls. This results in a higher percentage brine. The Bad Kösen graduation works is an industrial building of the 18th century and, like all graduation works, was used to extract salt by grading the brine. After the cessation of salt extraction, the preserved graduation works were largely used for medical purposes. From the realization of the healing and soothing effect of the brine, the spa business developed in many places around the turn of the century in our immediate vicinity to an economic sector not to be underestimated, even if only some of the bathing resorts that developed at that time could maintain the spa business until today. The Bad Kösen graduation house is about 320 m long, 18-20 m high and is located on the Rechenberg, a shell limestone rock in a north-south position. It was built around 1780 as a part of the Kösen salt works by the master builder Schröter according to the Senff's construction method. In 1809 the graduation house was extended by K.A. Henschel. During the spa season, the walkway is open to the public and is used for open-air inhalation. On some Sundays during the year, guided tours are offered on the upper deck of the graduation house. The fact that the entire saltworks complex with waterwheel, artificial rods, brine shaft and graduation house has been preserved as a coherent complex until today makes it unique in Europe.