Cagliari cathedral, commonly called the "Duomo", is described in detail and exhaustively by Manuela Manca, with attention to the explanation of every chapel in her website. Here, we reproduce only an extract, translated into English by Laurence Gambella; the rest is available by clicking on the button at the foot of the page.

Cagliari Cathedral is located in the Palazzo square, at the heart of the historic Castello district. It is flanked by the Archbishop's and Viceroy's Palaces. Its history spans a period of time from CXIIIth to the present day and reflects, in its stylistic and architectural features, the political, artistic and religious events of the city and of Sardinia.
The Pisans began the construction of the primitive church, dedicating it to Our Lady Assumed into Heaven, the same patronage as the cathedral of their city. (...)
The original Pisan construction was designed with three naves divided by eight monolithic marble columns, four on each side. The roofing of the central nave was made of wood, the two side naves with cross-vaults . After 1258, when the church was elevated to the rank of cathedral of the city, extension work commenced, with the building of the transept and the two side doors. This gave the construction a Latin cross form. From a C17th drawing we understand that the facade was also changed, with the opening of a great gothic mullioned window. The work carried out on the square bell-tower, which was almost certainly part of the original design, followed the same style. The Pisans left their work unfinished but begun again, and partly completed, by the new Aragonese overlords.
In 1326 the Army of the Infante Don Alphonsus of Aragon stormed the Castello fortress, driving out the Pisans.
Inside the cathedral there are still remnants of the original Pisan architecture:
a chapel consacrated to the "Sacred Heart of Jesus", to the left of the presbytery; the high altar; the internal counter-facade; the two pulpits positioned on either side of the central door, work of master William of Innsbruck, donated by the cathedral of Pisa in 1312; the lions on either side of the presbytery, part of the same ambo.
On the outside, there remain from the Pisan era: the two transept side doors; the architrave of the middle entrance door, decorated with a frame of acanthus and flowers; the bell-tower.
The Aragonese architects, in the retinue of the new conquerors, completed the construction of the chapel of the "Sacred Thorn" (also known as the "Aragonese Chapel" ), to the right of the presbytery, in the distinctive Gothic-Catalan style.

The construction of the dome between the central nave and the transept produced a wonderful, exquisitely baroque scenographic effect, illuminating the inside of the church from high up. This work unfortunately meant that the gothic transept chapels had to be sacrificed: to give stability to the walls on which the dome and vault rested, they were walled up and hidden by the funeral monuments of Archbishops Machin and De La Cabra. The original floor was likewise substituted with marble inlaying.
The cathedral was completed in 1674, exchanging its original Romano-Pisan style for the newer baroque. The desire to imitate the new design soon spread around the island, characterising the new buildings of worship which were built from then on.
The present appearance of the cathedral presbytery is owed to Archbishop Francisco Desquivel, who had it raised about a metre and a half above its initial level, to be able to build the Martyrs' sanctuary underneath. Construction began around 1618.
Access to the presbytery is via three sets of stairs, each with seven steps: one opposite the central nave, the other two in the side transepts. Built by the same Sicilian artists whom the archbishop entrusted with the building of the crypt, the presbytery is constructed in precious polychrome marble from Sicily. The balustrade surrounding it, built too in best-quality inlaid Sicilian marble is supported, at the base of the central stairway, by two magnificent styloforic lions. Another two felines are on either side of the presbytery. Originally, these formed part of William of Innsbruck's pulpit, donated by the cathedral Pisa in 1312 and subsequently dismantled during restoration work in CVIIth. The lions guarding the presbytery represent a rare example of Italian Romanesque and are unique in Sardinia. Sculpted with great realism (noteworthy for the time) and with minute attention to anatomical detail, they symbolise the Gospels (or Divine Wisdom) which defeats heresy. The lion to the right of the presbytery is fighting a dragon. The one on the left is attacking a young deer (or perhaps a horse) and a man, both without heads. Of the two styloforic lions who guard the staircase, one is fighting against a bear, the other throwing to the ground a bull. The duomo presbytery, raised up and surrounded by a marble balustrade was redefined in the following centuries in many island churches, as well as those without crypt or underground sanctuary. It was copied especially around the end of the C17th and the course of the 18th when the taste for baroque spread throughout Sardinia.
After the visit to the presbytery we cannot but admire the magnificent silver chandelier hanging from the dome, work of the local silversmith Giovanni Mameli and the precious tabernacle, also in silver, donated to the cathedral by the civil administration in 1610.
The high altar originated in the primitive church of St Mary and is decorated with a beautiful silver antependium, embossed and finely chiselled. The second portable altar, coming from the small church of Ss Laurence and Pancras. in the centre of the presbytery, is also covered with a gilded wooden antependium decorated with bas- reliefs.
On the right wall of the presbytery, on the same side as the steps, a marble sideboard is placed as an altar. This was built in 1702 through Canon Pietro Sanna, as the inscription at the foot of the altar recounts. The sideboard was used to hold the sacred objects used during the Mass. It is decorated with numerous cherub figures (eight in all), two of which fly around the medallion on which the bas-relief image of St Cecilia is sculpted.
Behind the high altar is the choir, covered between 1842-45 with frescoes by the Sardinian Antonio Caboni who painted the "Glory of St Cecilia" there.
The presbytery is illuminated by the light which penetrates from the three windows behind, and above it by the dome, producing an exquisite baroque show of lights.

To read the original italian text by Manuela Manca press the button

To consult the Cathedral official sitefrom where we extracted the photos of the interior (© Parrochia di S. Cecilia - Cattedrale di Cagliari, 1999 - 2002) by don Dino and by don Tonio Pittau, press the botton