Graduation tower

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A graduation tower consists of a wooden wall-like frame which is stuffed with bundles of brushwood. It increases the concentration of a solution of mineral salts. The salty water runs down the tower, and — through the action of breeze and sun — partly evaporates; at the same time certain mineral content of the solution are left behind on the sticks of brushwood. World's biggest and most famous complex of graduation towers is in Ciechocinek, Poland. This magnificent 100% wooden construction was erected in 19th century by Stanislaw Staszic. It consist of 3 graduation towers of total length over 2 km.