Chaves is a city and a municipality in the north of Portugal. It is 10 km south of the Spanish border and 22 km south of Verín (Spain). The population in 2011 was 41,243. The municipality is the second most populous of the district of Vila Real (the district capital, Vila Real, is 60 km south on the A24 motorway). With origins in the Roman civitas Aquæ Flaviæ, Chaves has developed into a regional center. The urban area has 17,535 residents (2001).

Mineral waters are the clearest evidence of these recent tectonic fractures. The Penacova-Régua-Verín Fault, is an active formation that extends longitudinally for 500 kilometres, intermingled with other faults resulting in subterranean hydrology. The thermal springs, principally those in Campilho and Salus Vidago (in Vila de Vidago) have developed from this mixture of circumstances. These mineral springs (bicarbonates, sodium, silicates and fluoride) in the vicinity of the city of Chaves, have provided a potential source of income.

The hot springs (Portuguese: Caldas) were known since the Roman period, when the town was 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 modern spa industry in Chaves use these waters for numerous treatments, including stomach, liver, intestinal, and kidney ailments, through oral ingestion. Many small guesthouses in the old part of the town are dependent on the influx of these visitors. The thermal spas are located between the castle and the river, in front of a large area of grass-covered park with playgrounds and tennis courts.