Aquæ Flaviæ was a major city in the Roman province of Gallaecia, an important and strategic post, where three of the most important Roman roads converged: the roads to Bracara Augusta, Asturica and Lamecum. There was much movement between Bracara Augusta and Asturica, for the region had natural resources that were exported to Rome.
Trajan's bridge over the river is a Roman monument that persists. It was built between the 1st and 2nd centuries AD.
The bridge has a board with 140 metres in length[clarification needed], supported by twelve visible arches, with other six not visible (buried by houses). It is the main symbol of the modern city of Chaves. When the town received the charter of Manuel I, the bridge was represented in the coat of arms.
The bridge has two middle columns with inscriptions regarding its construction.
One is from the time of Vespasian (known as Padrão dos Povos - Column of the Peoples) and mentions the civitates dependant of Aquae Flaviae: Aquiflavienses, Avobrigenses, Bibali, Coelerni, Equaesi, Interamici, Limici, Naebisoci, Querquerni and Tamagani. The Roman legion Legio VII Gemina Felix is also mentioned.
Transcription: IMP(eratori) CAES(ari) VESP(asiano) AVG(usto) PONT(ifici)/ MAX(imo) TRIB(unicia) POT(estate) X IMP(eratori) XX P(atri) P(atriae) CO(n)S(uli) IX/ IMP(eratori) VESP(asiano) CAES(ari) AVG(usti) F(ilio) PONT(ifici) TRIB(unicia)/ POT(estate) VIII IMP(eratori) XIIII CO(n)S(uli) VI[I]/ (...)/ C(aio) CALPETANO RANTIO QUIRINALI/ VAL(erio) FESTO LEG(ato) AVG(usti) PR(o) PR(aetore)/ D(ecimo) CORNELIO MAECIANO LEG(ato) AVG (usti)/ L(ucio) ARRVNTIO MAX(imo) PROC(uratori) AVG(usti)/ LEG(io) VII GEM(ina) FEL(ix)/ CIVITATES X/ AQVIFLAVIENSES AVOBRIGENS (es)/ BIBALI COELERNI EQVAESI/ INTERAMICI LIMICI NAEBISOCI/ QUERQVERNI TAMAGANI
Another (Column of Trajan) dates from the Trajan reign (104 DC).
Transcription: IMP(eratori) CAES(ari) NERVA/ TRAIANO AVG(usto) GERM(anico)/ DACICO PONT(ifici) MAX(imo)/ TRIB(unicia) POT(estate) CO(n)S(ule) V P(atri) P(ATRIAE)/ AQVIFLAVIENSES/ PONTE LAPIDEVM/ DE SUO F(aciendum) C(uraverunt)
Also famous was the Roman bath, which is believed to have lasted until the 16th century. The original structures, including two large pools, still intact and fed by hot springs, were discovered in 2006 and excavated until 2009. This spa complex has been dated from the 3rd century AD.