[4] Remnants discovered in Mairos, Pastoria and São Lourenço, those associated with transient proto-historic settlements and castros, show a human presence in the Alto Tâmega dating to the Chalcolithic.

[4] The region has seen persistent human settlement since Roman legions conquered and occupied the fertile valley of the Tâmega River, constructing a nascent outpost and taking over the existing castros in the area.

Artefacts from the area around the Matriz church indicate that Aquae Flaviae's centre was located in this place, in addition to an ancient headstone showing gladiatorial combat.

[4][6] Rome's hegemony lasted until the 3rd century, when, successively, the proto-Germanic tribes of the Suebi and Visigoths as well as the Alani colonized the imperial settlements of Chaves.

[7] Barbarian dominion lasted until the Moors invaded from North Africa, defeating the Visigoth King Roderic at the beginning of the 8th century.

[10] Battles between the Christians and Muslim forces then continued until the 11th century, when Alfonso V of León permanently reconquered Coimbra, establishing a firm buffer-zone to the south.

[4] Owing to its geographic location (on Portugal's northern frontier with Spain), King Denis, ordered the construction of a castle to protect the kingdom's border.

[4] During the reign of Afonso II, when the king continued to provoke the ire of the Papacy, Portuguese knights attacked the Galician tenancy of his half-brother Martin Sanches (who lived in the kingdom of Alfonso IX of León), possibly since the Bishop of Braga had estates in that region.

[11] At the same time, Alfonso IX of León seized Chaves, which remained in Leonese hands until the reign of King Sancho II, when he and Ferdinand III met in 1230/1231.

[13] The remnants of the Roman baths, and the houses used to assist the invalid, were demolished by the Count of Mesquitella at the end of the 17th century, in order to reinforce the defense of Chaves.

[4] Chaves was also a site of various religious apparitions, during the decade of 1830, eventually resulting in the construction of the Santuário da Nossa Senhora Aparecida (Portuguese: Sanctuary of Our Lady Revealed).

Chaves is one of the six municipalities of the Alto Tâmega, situated in the district of Vila Real, strategically positioned in the northwest of the Iberian peninsula and accessed by important international highways.

The region is dominated by the Quaternary Chaves sedimentary basin, a graben aligned on a north-northeast to south-southwest orientation bounded by the Hercynian massif and metamorphic schistose formations.

[19] Mixed with the schistose complex, there are bands of graphitic slates, mainly in the southern part of the urbanized area of Chaves and south-east of Faiões.

One of the oldest formations in the region, it dates back to the Ordovician period ( between 488.3±1.7 to 443.7±1.5 million years ago), is composed of schist and graywacke deposits.

With temperatures reaching 73 °C (163 °F), these mineral springs (bicarbonates, sodium, silicates and fluoride) in the vicinity of the city of Chaves, have provided a potential source of income.

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).

The modern spa industry in Chaves use these waters for numerous treatments, including stomach, liver, intestinal, and kidney ailments, through oral ingestion.

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.

Fog often hovers over the valley during the winter, usually lifting by midday, but on rare occasions can last for days, and can potentiate the development of rime ice.

Chaves was built, destroyed, and rebuilt several times by either faction (Christian and Muslim), when they occupied the castle (it is likely that for some periods the town was completely abandoned).

While the walls were eventually rebuilt, the advent of artillery would make the castle's fortifications obsolete, and its importance waned, while the historical battlements fell into ruins.

Since the land can be irrigated with canals there is intensive farming of potatoes, corn, rye, hay, while plots of vegetables are also commonplace in the local market.

It is serviced by A24 motorway, which links Chaves with the south, to Viseu, Coimbra and Figueira da Foz, connecting to Vila Pouca de Aguiar by the A7 (which acts as the gateway to the southern Trás-os-Montes), and the N103 from Bragança to Braga.

In addition to the old Church of São Francisco (which for three centuries was resting place of the first Duke of Braganza), there are other buildings which have been artistically converted into hotel rooms, and which served the army as barracks for many years.