Federal sanctuary of the three Gauls

The Sanctuary of the Three Gauls (Tres Galliae) was the focal structure within an administrative and religious complex established by Rome in the very late 1st century BC at Lugdunum (the site of modern Lyon in France). Its institution served to federalise and Romanise Gallia Comata as an Imperial province under Augustus, following the Gallic Wars of his predecessor Julius Caesar. The distinctively Gallo-Roman development of the Imperial sanctuary and its surrounding complex are well attested by literary, epigraphic, numismatic and archaeological evidence.

The Imperial cult sanctuary at Lugdunum was the earliest and most important institution of its kind in the Western Roman empire. Its establishment at the junction of three new Imperial provinces, later collectively known as Tres Galliae (the Three Gauls), embodied a policy of integrated military, civil and religious settlement among the unstable Western provinces of the newly established Principate. It was founded by Drusus in rapid response to a rebellion provoked by the census of Gallia Comata ("long-haired" Gaul) in 12 BC.

Lugdunum provided a centralised, permanent base for the Imperial governorships of Gallia Aquitania, Gallia Belgica and Gallia Lugdunensis, and an annual, Roman-style (council) for their provincial elites, based on existing Gallic political and religious practices. The monumentally lavish and comprehensively Roman development of the Sanctuary and its associated buildings provided a context for the acculturation of a new Romano-Gallic polity under the pax Romana, in which the Roman military maintained a relatively discreet local presence.

As stepson to Augustus, Drusus represented the Imperial family and as provincial governor, he was also augur. The inaugural day of the sanctuary – August 1 of either 10 BC or 12 BC – was important to both Romans and Gauls. August – formerly Sextilis in the Roman calendar – had been renamed in honour of Augustus, and its kalends (the first day of the month) was particularly auspicious as the anniversary of his victory at Alexandria. In the Gallo-celtic calendar, the same day was sacred to the sun-god Lugh, who may have been venerated on the Fourvière hill at Lugdunum, though no temple has been found. As a sun-god, Lugh could be identified with Roman Sol, Apollo and the Augustan-Stoic concept of the Imperial "saviour" as the "second sun". A foundation (or an inauguration) in 12 BC would have coincided with Augustus' assumption of office as pontifex maximus. The ara (altar) was dedicated to Dea Roma and Augustus and its first high priest (sacerdos) was Caius Julius Vercondaridubnus, a Gaul of the Aeduan elite. His name indicates his Roman citizenship and Gallic origins - his election to Imperial priesthood may confirm a preference based on his personal standing and that of his civitas as fratres ("brothers", or allies) of Rome.

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