The Cathedral, dedicated to the Virgin Mary's Assumption into heaven, is a grand structure formed in different styles, due to the various stages of construction.

Built in 1185 by Archbishop archbishop Gualtiero Offamilio first basilica in the area that the Saracens had turned into a mosque, has undergone several renovations over the centuries, the last is at the end of XVIII century, when, at the structural consolidation, it radically remade the interior designed by Ferdinando Fuga.

In 1767 in fact, the archbishop Filangieri had commissioned Ferdinando Fuga a restoration of the building, intended only to strengthen the structure. The work was begun only in 1781, but performed no escape from Palermo by Giuseppe Venanzio Marvuglia and lasted until the nineteenth century also. The remaking of Marvuglia were actually much more invasive and radical projects of the Florentine architect, thought that instead of preserving, at least in part, the complex longitudinal aisles and the original wooden ceiling. The restoration intervened to change the appearance of the complex, giving the church but discordant feature dome, performed according to the will of the Fugue. It was on this occasion that destroyed valuable forum that Antonello Gagini had raised at the beginning of the sixteenth century and was decorated with statues, friezes and reliefs. Even the colorful tiled domes to cover the rebuilding of the aisles back in 1781.
The right side of the building, with advanced features turrets and a large Gothic-Catalan style portico (the current access), built around 1465, overlooks the square. The portal of this entrance is a magnificent work of Antonio Gambara, performed in 1426, while the beautiful wooden doors are of Miranda (1432). The Madonna is a mosaic of the thirteenth century, the two monuments on the walls, works from the early eighteenth century, Charles III of Bourbon are right and Vittorio Amedeo II of Savoy on the left.

The apse is squeezed between the towers is the most original of the twelfth century, while the most tampered with is the left side, where there is a beautiful portal Gaginesque the early sixteenth century.
The south-west facade, which looks at the archbishop's residence, should be reported to the fourteenth and fifteenth centuries.

The interior has a Latin cross with three naves divided by pillars. In the first two chapels of the right aisle are the tombs of emperors and royal settled there in the eighteenth century, after the restoration, which moved from their original site, however, was in the same basilica.

Roman sarcophagus in place on the right wall, there are the remains of Constance, sister of the King of Aragon and wife of Frederick II, who died in 1222. The polls, in profile under the canopy, are Henry VI, who died in 1197 (right) and Frederick II, who died in 1250 (left). Here are also contained the remains of Peter II of Aragon, who died in 1338. In the background, under the canopy mosaic, there are the tombs of Roger II, who died in 1154, and his daughter Constance, who died in 1198. The latter two are the ones that originally were in the transept of the Cathedral of Cefalu.

To the right of the presbytery is the chapel of Santa Rosalia, patron saint of Palermo, and the urn containing the relics of silver, seventeenth-century work of Matthew Lo Castro, Francesco Giancola Ruvolo and Viviano. The two reliefs of Valerio Villareale, are: Santa Rosalia Christ calls for the release of the plague and the entrance of the glorious relics of Santa Rosalia in Palermo

In addition to the choir stalls in Gothic-Catalan in 1466 and the marble remains of the grandstand Gagini adapted, high artistic interest is the marble statue of the Madonna and Child by Francesco Laurana, performed together with other aid in 1469, the precious holy water (placed at Pillar IV) and uncertain work of Domenico Gagini the Madonna della Scala performed in 1503 by Antonello Gagini and placed on the altar of the sacristy