This is a beautiful Romanesque-Gothic building linked to an ancient legend, which tells that Charlemagne—terrified by the sudden appearance of three ghostly skeletons—was saved by the Virgin Mary, to whom he decided to dedicate an abbey on the very spot where the event took place. In reality, there is no definitive information about the building prior to the end of the 11th century. The façade features an elegant portal with a carved lunette, three tiers of blind arcades, a double-arched window (bifora), and various statues. Inside, the carved and painted narthex is supported by Gothic arches; the high altar boasts a magnificent polychrome terracotta triptych; and in the apse, two bas-reliefs—still bearing traces of their original color—depict the Virgin Mary and the Archangel Gabriel at the moment of the Annunciation. Finally, the cloister, with its pointed arches, contains fine capitals and an important cycle of frescoes, including a depiction of the "Three Living and the Three Dead"—a direct reference to the legend.