Thermal waters have been used from ancient times. From those early experiences and the consecutive improvements in the understanding and treatment of these waters, all around the world different cultures and communities have used natural structures or have built facilities for the best use and exploitation of the mineral spring water. Nowadays thermal spas, inheritors of a rich and long tradition from the ancient world, combine classical techniques with innovative proposals. Thus, the introduction and implementation of new technologies in bathtubs, swimming pools, showers, saunas, etc., allow the efficient optimization of thermal techniques and hydrotherapy facilities. Moreover, the development of health tourism offers a new way to understand the use of thermal water, which requires higher quality and specialization of the spa services. Every year thousands of people travel to Europe for a healthy holiday and to improve their welfare and wellbeing. Resorts, spas, thalassotherapy centers and thermal spas that use hot thermal water utilize bath techniques, respiratory applications, pressure techniques, wraps, etc. These techniques use facilities and amenities such as swimming pools, bathtubs, showers, sprays and stoves, among others. One can also find peloids (thermal mud) and any kind of clay and herbal wraps. From the practices developed in Roman times, but especially from the first hydrotherapy techniques described by Priessnitz until today, there have been numerous innovations that have enabled the spas to adapt to the demands and needs of a new type of customer. Nowadays, there are companies specializing in the design and innovation of hydrotherapy that favour the modernization of existing spas or the emergence of new spas. The highlights are control and automation; new materials; design and architecture designed by prestigious architects.