Graduation tower

A graduation tower (occasionally referred to as a thorn house[1]) is a structure, used in the production of salt, that removes water from a saline solution by evaporation, increasing its concentration of mineral salts.

The tower consists of a wooden wall-like frame stuffed with bundles of brushwood (typically blackthorn) that have to be changed every five to ten years, as they become encrusted with mineral deposits over time.

Graduation towers can be found in a number of spa towns, primarily in Germany but also Poland and Austria.

as having beneficial health effects similar to that of breathing in sea air.

[citation needed] Large graduation tower complexes are located in Ciechocinek and Inowrocław, Poland.