The secret of the health-giving properties of the waters was discovered long ago. The rich culture of thermal spas in Slovenia is shown by excavations of remains from the Roman empire and written documents about thermal waters from the 12th century, and particularly the foundation and expansion of existing health centres during the period of the rebirth of central European spas; thermal and climatic spas in Bled, Laško, Dobrna and Rogaška Slatina have - for more than a century and a half - intensively developed spa tourism, which has developed into one of the more important branches of Slovenia tourism.