Founded at the end of the 13th century, it was destroyed and enlarged several times until the 18th century, so that its plan has a Greek cross in the center, covered by an octagonal dome.
It was dedicated to Saint John the Baptist in 1528 and erected as a cathedral by Gregory XIII in 1576. It contains exceptional works: an altarpiece from 1498, signed Barbagelata, depicts the Annunciation surrounded by saints and scenes from the life of the Virgin Mary on the predella.
The high altar, in polychrome marble in a very elegant Ligurian Renaissance style, was donated by a Calvian family in the 17th century.
On the left is the Rosary Altar, also in polychrome marble, a highly venerated processional statue: the Virgin of the Rosary, who came from Spain in the sixteenth century.
In counterpart, a lustro stucco altar represents the Black Christ of Miracles, made of painted wood of Florentine workmanship, enriched with a perizonium in embossed silver, whose strong popular piety made the victory possible during the siege of 1555.
An important marble baptistery, donated in 1569 by Giovan Antonio Vincentello, testifies to the enrichment of some Calvi emigrants in the New World.
A gilded wooden pulpit dating from 1757 completes this beautiful architectural testimony of Baroque art.