Les Carrières de molasse

The comparative softness of the rock has allowed a set of dwellings to be hollowed out at the foot of the Molasse sandstone hill. About a hundred cavities, from various eras, have been identified. While most are concealed by modern houses.

Exploited since Antiquity, these quarries supplied materials for major medieval construction projects such as Valence cathedral and the collegiate church of Saint-Barnard in Romans. Still used for the construction of the Bourne canal in 1877, molasse went into irreversible decline from that time onwards, notably due to competition from cement.

Although no longer in operation, many quarries can still be visited, the main one at the entrance to Châteauneuf-sur-Isère.