The Patriarchal Cathedral Basilica of Saint Mark, popularly known as Saint Mark’s Basilica, is located at the eastern end of the Piazza San Marco, adjacent and connected to the Doge’s Palace, the residential palace of the supreme authority of the former Venetian Republic. Considered as one of the best known examples of Italo-Byzantine architecture, it is the cathedral church of the Roman Catholic Archdiocese of Venice and one of the famous landmarks of the city.

The first building of St Mark, consecrated in 832, was founded as a ministerial structure to house the remains of St Mark that had been smuggled out of Alexandria by two Venetian merchants in a barrel of pork fat, to avoid the inspection of the customs officers, as the Islamic religion hates pork meat.

Thereupon, St Mark replaced St Theodore as the patron saint of Venice and his attribute of a winged lion later became the official symbol of the Venetian Republic. However, the building was burned in 976 during a popular revolt against the doge (chief magistrate) Pietro Candiano IV, which was subsequently restored by his successor.

It is estimated that the construction of the present Basilica was completed in 1071. While the exterior of the basilica, surmounted by five domes, reflects the mixture of Italian and Byzantine features, it is laid out in the design of a Greek cross design, with each arm of the cross divided into three naves with a dome of its own as well as the main dome above the crossing. Each of the five domes, borne on huge pillars, is almost 13 m in diameter and has 16 windows.

The exterior of the Basilica is elaborately ornate, which has been added to over the centuries and the additions of sculpture, mosaics and ceremonial objects have gradually increased its granger. It can be mentioned here that the famed four bronze horses on the west facade gallery, were brought to Venice from the Hippodrome of Constantinople, at the time of the Fourth Crusade in1204, where they had been part of a Greco-Roman triumphal Quadriga, a sculpture of a chariot drawn by four horses abreast. They were set up in the Arsenal, on the exterior of San Marco in 1254, but were subsequently removed and taken to Paris by Napoleon. When they were returned in 1815, the originals were kept in the museum of the Basilica and replicas were placed in their place.

The exterior of the basilica consists of three registers, namely the lower, upper and the domes. The centre of the lower register is slightly larger among its five arched portals, surrounded by columns. The Narthex is approachable through large bronze doors. While the mosaics above the lateral portals display the stories of St. Mark's relics, the mosaics in the upper level arches depict stories from the life of Jesus, which include the gilded mosaic of the famous ‘Last Judgment’, above the main portal.

The large central window is crowned with the Winged Lion, the symbol of Venice and the statues at the top of the central portal depict Saint Mark and the angels. The statue of the Four Tetrarchs, representing the inter-dependence of the four Roman rulers, who ruled under the co-emperor plan, was also brought from Constantinople in 1204 and was placed in the southwest corner of the Basilica. 

The interior of Saint Mark’s Basilica is even more spectacular than the building's exterior. Arranged in a geometric pattern with interspersed animal designs, the amazing floor of inlaid marble and glass simply glow in the restricted light. Completed in the twelfth century, the walls and ceilings of the basilica, covering an area of around 8,000 square metres, are decorated with astounding gilded mosaics. The screen separating the choir from the nave, bedecked with immaculate marble statues, represents a perfect piece of Venetian Gothic sculpture, created by Jacobello and Pier Paolo dalle Masegne.

The Pala d'Oro or the Golden Pall, the high altar retable of the Basilica di San Marco in Venice, is made of gold and silver and ornamented with different types of precious stones, in addition to several enamels depicting various saints. Subsequently, it was renovated and extended several times and the work continued over five centuries, as new elements were added. The Tesoro or treasury, situated to the right of the main altar, contains many of the invaluable items brought from Constantinople, along with other important relics that the church has gathered over the years.