Ciechocinek is a health resort on the River Vistula, and the location of some of Europe’s outstanding timber structures. New brine springs were discovered in the area in the early 19th century and the mining engineer Jakub Graff designed three graduation towers, built in 1827-8, 1833 and 1859, respectively 648 m, 719 m and 333 m long, and more than 15 m high. They were constructed of oak and filled with faggots of blackthorn. Brine was pumped to the tops by two windmills and concentrated as it percolated through masses of blackthorn twigs, releasing ozone and iodine. The iodine-rich atmosphere is used as part of some of the health cures available in the resort.