Chaves - Hydrothermal springs

The hot springs (Portuguese: Caldas) were known since the Roman period, when the town was called Aquae Flaviae; the Waters of Flavius were an important social gathering point, but fell into disuse as the town was slowly abandoned by attacks. The spas belong to a vast area of hydrothermal springs that stretch from Verín (in Galicia) to Pedras Salgadas, 30 km from Chaves (on the road to Vila Real). Despite its vastness and abundance of water, this thermal system is little utilized; of the nine groups of thermal springs there are only adequate installations in four of them: Chaves, Carvalhelhos, Vidago, Pedras Salgadas, and Verín.
The waters of the spring, that are captured in three springs within Chaves, have mean temperatures of 73 °C (163 °F) (the hottest bicarbonate waters in Europe).
These values are still valid as you can read on the Cautionary Label above.