The mineral hot spring waters of São Pedro do Sul originates in a deep failure by the thermal baths. The thermal waters emerge at 67°C a 18 l/s debit and pH 9.8 and are related, at regional level, with the active fault Verin-Penacova and, locally, by the contact between granitic rocks and ante-Ordovician schists. The emergencies of natural radioactive sulfur mineral water are used for room heating, for sanitary hot water purposes and, finally, for medicinal applications. It is currently considered one of the most modern spa resorts in Europe, having qualified technical and human resources, and facilities equipped with the latest technology in the area of Spa therapy, counting over 20,000 visitors a year. Its thermal waters are exploited since antiquity, as demonstrated by existing Roman ruins in the heart of the Spa complex.
The thermal baths of São Pedro do Sul are located on the Vouga river banks, a medium-sized river which rises in the Lapa mountain and flows into the sea in Aveiro city. On its way through the hot springs, it is a river that maintains a well-preserved riparian gallery and some beautiful oaks in the vicinity. The royal fern and the hard-fern show us the good state of preservation of these ecosystems and the river cruisers, a very rare dragonfly in Europe, can be easily observed.Butterflies are here frequent and diverse, highlighting the camberwell beauty butterfly, the spanish festoon, the lesser purple emperor (very rare in Portugal) and the white admiral. The playful otter hunts often in these parts, and the iberian emerald lizard is always present on trails and walls along the river. The common kingfisher constantly patrol the waters of the Vouga river, in search of small fish on which it feeds.
The roman thermal baths of São Pedro do Sul have their origin in the first century D.C. and were classified as National Monument in 2008. Better known as “bath” or “Caldas de Lafões”, they represent one of roman’s best preserved thermal complex in Portugal. Noteworthy is the remnant part of the old “balneum”, with part of the roman pool and large columns of granite. It is thought that it would have an area of cold baths – “frigidarium” – and the pool, which is called today D. Afonso Henriques (1st king of Portugal) pool, which is in perfect condition. In the twelfth century they were used by the most favored classes, especially the presence of the 1st king of Portugal for treatment of a fracture suffered in the ill-fated Battle of Badajoz. During the reign of King Manuel I was built up the Royal Hospital of Caldas de Lafões and in 1884 was built the bathhouse Queen Dona Amélia. In 1987 it was built the bathhouse of D. Afonso Henriques, in honor of the 1st king of Portugal.
