The cathedral represents the fulcrum of the historic center of Alghero, a town that has maintained a strong Catalan cultural identity.
With the “Bolla Aequum reputamus”, prepared by Alexander VI but promulgated on 26 November 1503 by Pope Julius II, Philip II's request to reform the ancient Sardinian dioceses was accepted. In 1495, the sovereign submitted to the Holy See a project for the revision of the Sardinian ecclesiastical jurisdiction, which contemplated the reduction of the number of dioceses.
Since the reform of 1503, the ancient dioceses of Bisarcio, Castro and Ottana were merged into a single district with a new headquarters in Alghero.
The stronghold, elevated to the rank of city by the king in 1501 also because of the new role it should have played, for a long time did not have a building worthy of serving as a cathedral.
The first bishop, Pietro Parente, appointed in 1504, resided in Sassari and not even the following, until Durante dei Duranti (1538-41), resided in the new diocese without a cathedral, whose factory was started only in the third decade of the 16th century and carried on amid a thousand difficulties, often of an economic nature.
It is assumed that by 1547, the choir with the five circular radial chapels and the octagonal barrel bell tower that rises above the central chapel of the gallery, with the underlying façade with the lily portal, following the now consolidated Elizabethan model of Catalan cathedrals, of Barcelona in particular. Subsequently, work slowed down and resumed with renewed vigor under the bishopric of Monsignor Pietro Perez del Frago, elected in 1566. A few years earlier, an Italian or classicist architect - perhaps Rocco Capellino himself, a military engineer in Sardinia starting in 1552 with the aim of adapting the island's fortresses to the new war techniques - made a Renaissance turn to the construction.
Of the five radial chapels that make up the girdle, the first from s., with a rectangular plan and vaulted without ribs with renaissance-inspired legs, must be considered the last one executed in chronological order, when the new architectural concept of classicism took over. From this moment on, the work will continue according to a late Renaissance design that included a large longitudinal room divided into three naves and joined the Gothic body by means of a vast transept.
Bishop Bacallar's ordinations, on September 18, 1593, testify to the consecration of the building even though the factory could not be said to have actually been completed until around the middle of the 17th century. In 1638, in fact, the transept and the cruise were covered, which were turned respectively into a pavilion and an octagonal dome on a tall windowed drum.
The naves had already been turned over at the end of the previous century, most with a slightly lowered barrel vault set on a ledge supported by large classical shelves and marked by sub-arches that divide the space below into bays. The minimal difference in the orthogonal arms gives the longitudinal structure a Renaissance centrality, highlighted by the accentuated development in height of the naves.
The bell tower, with an octagonal barrel crowned by a pyramidal spire, is part of a common type in Catalonia (Sant'Agata chapel and Barcelona cathedral).
Among the marble furnishings, due to late 18th century baroque overlays, the pulpit and the monumental high altar by Giuseppe Massetti from Genoa (1727) are valuable.
The neoclassical pronaos is the result of the nineteenth-century reconstruction of the original late-Renaissance façade.

History of studies
The church is the subject of study in the volume by Francesca Segni Pulvirenti and Aldo Sari on late Gothic and Renaissance architecture (1994) and by Salvatore Naitza on late seventeenth-century and purist architecture (1992).

Bibliography of
S. Naitza, Architecture from the late 17th century to purist classicism. Nuoro, Ilisso, 1992, sheet 64;
F. Segni Pulvirenti - A. Sari, Late Gothic and Renaissance Architecture. Nuoro, Ilisso, 1994, sheet 32.

How to get
There On the Magellano waterfront, in the narrow stretch between the “de Castilla” and the “de la Magdalena” tower, the Porta a Mare opens, leading to the Civic Square. From here, on the right, you pass into the small square of the Duomo, where the cathedral of Algherooverlooks.