Founded around 870 and attached to Cluny around 930, Charlieu Abbey became a priory. In the 12C, it was treated to the joint efforts of the architects and artists of Cluny and the help of Philippe Auguste, its benefactor, who had it fortified. Excavation has revealed a series of constructions, while a lapidary museum and a religious art museum display major pieces found on the site. Don't miss the north façade, whose massive 12C porch is a masterpiece of Romanesque art.