Duomo di San MarcoThe first factory of the Cathedral of San Marco was probably built on the site of an older chapel, in an era prior to 1278, when, for having assumed an increasingly important and independent role, it detached itself from the mother church of Torre.

The first church consisted of a single nave, with three apse chapels with a square plan, the larger central one and the left one with thicker walls, perhaps because the bell tower had been placed on top of it. During the first half of the fourteenth century, in relation to the great development of the city, a project of considerable expansion of the building towards the apse area was conceived, a transept-tiburio supported by imposing octagonal pillars, a hall with three naves, and the construction of the bell tower, certainly completed in 1347. The original project of a larger church, however, was interrupted and, due to the lack of means, it was limited to joining the new apse area with the ancient nave that remained unique. During the second half of the fourteenth century the efforts were concentrated mainly in the interior decorative apparatus of which some fragments remain. Between the end of the 14th and the first half of the 15th century the chapels of the Blessed Sacrament and the Saints Peter and Paul (1420), then frescoed, and the Montereale Mantica chapel (1478) were realized. In the 16th century, were called to decorative works famous artists such as the Pilacorte (1511 portal of the facade, holy water font and baptismal font), Pordenone (Pala di San Marco, Pala della Misericordia, 1515-16, fresco of San Rocco and Sant'Erasmo, Madonna col Bambino, Portelle del Battistero) and Calderari (Cappella Mantica). Around 1591-1593 the six chapels on the side of the nave or altars were built, subtracting outside a part of the cemetery area.

It was only in the 18th century that the nave was raised, with the introduction of a new giant order of Corinthian pilasters and superimposed trabeation and the enlargement (1724-1741) of the six side chapels, replacing the smaller ones, connected to each other with passages in order to remember the structure of the minor naves.

Also in the eighteenth century there were other interventions of restoration, extension and enlargement of the tiburio, closing of the windows of the facade and of repaving the nave.

In 1840 the architect Francesco Lazzari was called to design a new conformation of the facade which, however, was only partially realized (base and four semi-columns), leaving the design intervention halfway done.

Subsequent interventions, even after the earthquake of 1976, concerned the consolidation and restoration of different parts of the building, allowing the recognition of the architectural structures and the oldest fresco decorations.