Contiguous to the archaeological museum of Montbrison, in the Loire, the museum of La Diana presents a heraldic room of impressive dimensions with its 19 m long and 8 m high. Arranged at the end of the 13th century, it reveals to its visitors a pointed vault in third point decorated with forty-eight parallel bands themselves decorated with crests and fantastic animals which represent the feudal families allied with the counts of Forez.
Reworked in the 19th century in a neo-Gothic style, the facades also deserve our attention with their elegance reminiscent of the architecture of Viollet-le-Duc. Since the end of the 19th century, the room of La Diana has housed an archaeological museum with important collections of objects from Prehistory, the Gallo-Roman period, the Middle Ages or the modern period, as well as pieces related to numismatics, calligraphy, heraldry or ceramology.