The founding of a hospital, in 1485, by Queen D. Leonor, the wife of King D. João II, was a complex political operation, aimed at creating out a settlement and a pioneering, world-first enterprise, where the fi nest artistic and technical resources were employed at the service of the Realm’s strategic objective, bringing about one of the earliest manifestations of European Humanism. From that moment on, and throughout its many modifications, the Thermal Hospital has remained an element of scientific and historical interest, both as a piece of thermal architecture and hydraulic engineering and as a structuring element in urban development. At the same time, we underline its connection to the cult of water and the assistance support to the most disadvantaged, which gives it an immaterial value with great significance through the ages. This text presents the uniqueness, authenticity and historical exceptionality of the Thermal Hospital of Caldas da Rainha, as well as the intention to defi ne a network of hospitals to support a joint application to UNESCO.