Rebuilt in the same place where the previous church stood, destroyed in 1176, the cathedral was finished in 1227 when the architect Giorgio da Como certified its completion, as indicated by a plaque placed at the south entrance. The cathedral today still has its original Istrian stone facade while the body of the church was completely rebuilt in 1781 based on a project by the architect Cosimo Morelli. Inside, the foundations of the ancient paleochristian basilica and the eighteenth-century crypt can be visited.