Bishop Giovanni Barozzi commissioned the re-building of the cathedral of St. Vincent in the mid-15th century, for the plans of which Filarete claimed credit.
Finally Bishop Gregorio Barbarigo succeeded in obtaining from Pope Innocent XI the bull Exponi nobis of 18 August 1697, which established for the diocese a single chapter and a single cathedral, changing the dedication of the surviving cathedral to Saint Alexander from Saint Vincent.
The church also contains a Madonna with child with two doves by Giovanni Cariani, as well as canvases attributed to Giambettino Cignaroli and Sebastiano Ricci, including a Saints Firmus, Rusticus, and Proculus (1704).
Nearby stands the octagonal baptistery, constructed in 1340 by Giovanni da Campione for the Basilica of Santa Maria Maggiore.
Inside are bas-reliefs of episodes of the Life of Christ, a statue of John the Baptist and a font of 1340 by Giovanni da Campione.