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Origin and history

The temple of Mercury of the Duomo Puy, built in the 2nd century, replaces a first building of the 1st century that became too small to accommodate pilgrims. This Gallo-Roman place of worship, located at 1,465 m above sea level, was dedicated to Mercury Dumias, a syncretic divinity combining the Roman god with local Celtic traditions. The 19th century excavations, led by Louis-Clémentin Bruyerre, revealed a bronze tablet dedicated by Matutinius Victorinus, confirming the attribution of the sanctuary.

The temple was organized around a square cella preceded by a pronaos, typical of Gallo-Roman architectural syncretism, and rose on successive terraces intended to theatricalize the ascent of the faithful. Altars, statues and a treasure hall were complete together, while chapels marked the way from the pass of Ceyssat. The site's fame extended to Germania, as evidenced by the arverous votive inscriptions found in Miltenberg or Cologne, evoking a "Mercury King of the Arvernes".

Partially destroyed from the third century, the temple was rediscovered in 1872 when the meteorological observatory was built. Ranked a Historic Monument in 1889, it was the subject of intermittent excavation campaigns, notably at the beginning of the twentieth century by Auguste Audollent, who exhumed a statuette from Mercury. The modern restorations (2000–2018), carried out by Dominique Tardy and Jean-Louis Paillet, partially restored the southern walls and terraces, at a cost of 7 million euros. The site reopened to the public in 2024.

The sanctuary was part of an arborous cultural network including the temple of the Tourette d'Enval (Orcines) and the agglomeration of the Ceyssat Pass, where pilgrims could perform rites before the ascent. A colossal statue of Mercury, evoked by Pliny the Old as the work of the sculptor Zenodore (I century), could have adorned the first temple, although there is no archaeological trace of it. Grégoire de Tours also mentions a Vasso Galate whose identification with the Dôme puy remains debated.

Recent excavations have confirmed the economic importance of the site, with monetary offerings up to the fifth century and local trachyte quarries exploited for its construction. The temple thus illustrates the religious and political influence of Augustemetum (Clermont-Ferrand), capital of the Arvernes, where imperial worship and the Gaulish deities coexisted under the aegis of Rome.

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