The sombreness of the Herrera style.
It was built in the Herrera style with a single nave and several adjoining chapels. The main fronts of the cloister are from a pervious temple, from the 15th century, as is the bust-reliquary of Santa Felicitas.
The most important chapel is the Baroque-style Communion chapel with its beautiful main front. The altar of Saint Nicholas of Bari is also Baroque and is located in the apse of the central nave. The exterior of the procathedral is sombre with extraordinary greatness. The historic quarter, where it is located, contributes to this. There is an important series of grilles from the 18th century in the cloister, which was built in the mid-17th century. The steps of the high altar are made of marble from Genoa.