The largest church in Corsica. There is a unique nave, a five-span plan, and a deep choir. A vault with a medallion of the Baptism of Christ, gilded stucco, plaster, paintings. Side chapels with altars in polychrome marble. A wonderful altar in the chapel of St. Erasmus.
Paintings from the heritage of Fesh, mostly from the 18th century. The silver tabernacle and its counterpart date back to the 19th century. The 18th-century pulpit is amazing. The organ gallery is unique because of the shape of the "swallow's nest". The instrument is richly decorated with golden trophies.