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Origin and history

The Roman gate of Bons is an archaeological site located in the gorges of the Infernet, in the commune of Les Deux Alpes (Isère). These are the ruins of an arch partially carved in the schist and masonry, measuring 4.05 m tall and 3.50 m long. The track that crosses it, 2.45 m wide, has two parallel rudders that are deliberately dug into the rock. Its exact origin remains debated: some attribute it to antiquity (with comparisons at Donnas Gate in Aosta Valley), while others evoke a Renaissance construction. It was still intact in the 17th century, as evidenced by a 1660 engraving, but partially collapsed in the 18th century.

The gate is located halfway between Grenoble (former Cularo) and Briançon (Brigantio), on an ancient route through the Romanche valley. Its function remains uncertain: fortified gate (signs of herse are mentioned), road tunnel, triumphal arch or memorial. Remnants of the adjacent Roman route, identified on both sides of the building, suggest that it was part of a coherent set linking these two Alpine cities. It was listed as a historical monument on April 18, 2014.

The arch, surmounted by an elliptical vault, is entirely dug in chlorite shales. Its present state is the result of a gradual deterioration, especially in the eighteenth century. The track rudders, spaced 1.46 m apart, were not formed by wear but intentionally cut, which underscores the methodical nature of its construction. Several hypotheses remain about its use, although its integration into the Roman road network of the Cottienne Alps (between Mont-Cenis and Larche Pass) is attested by recent archaeological studies.

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