The Pisa Cathedral, dedicated to the Assumption of the Virgin Mary and the seat of the Archbishop of Pisa, is the largest and the oldest structure in Piazza dei Miracoli in Pisa, Italy, a plaza which contains a world-famous ensemble of several magnificent structures, including the famous leaning bell tower and Pisa Baptistery.

In the middle Ages, before the silt deposits of the River Arno pushed the sea away, Pisa was located very near the coast and was an important port city. Later, it became a city-state, with its economy strongly based on maritime trade. In those days they keenly competed with the other Italian naval powerhouses like Genoa, Venice and Amalfi, to dominate Mediterranean trade. Apart from that they were almost constantly engaged in fighting with the other rival maritime powers in Corsica, Sicily and North Africa. In fact, in 1063 the fleet of Pisa defeated the Saracens in Palermo, the capital city of Sicily and the spoils plundered from the Muslims provided the necessary fund to start the construction of the Pisa Cathedral.

The Pisa Cathedral complex, an assemblage of freestanding buildings, containing the cathedral, baptistery and the bell tower, which later became famous as the Leaning Tower of Pisa, is unusually situated well outside the city walls, surrounded by the marshes of the Arno, in the area of the old city cemetery. The dampness of the soil of the site made the ground under the base of the key structures of the complex unstable, which is most noticeable in the campanile or the bell tower, which began to lean even while it was still being built in the twelfth century.

Considered as a notable example of Pisan Romanesque style, the Pisa Cathedral reflects a combination of Islamic architecture, Byzantine features and Lombard decoration. Founded in 1064, it was declared a primatial church in 1092 and consecrated with great pomp by Pope Gelasius II on 26 September 1118.The present appearance of the  structure is the result of numerous restoration campaigns that were carried out in different periods. Architect Buscheto created the original layout with four aisles and one nave, a transept with one nave and two aisles and the dome on the cross. Later, the length of the nave was increased by Rainaldo in the early 12th century, by adding three bays, consistent with the original style of Buscheto and also enlarged the transept. He also planned a new facade which was completed under the direction of the sculptors Guglielmo and Biduino. However, the building was not finally completed until the last quarter of the 12th century, when Bonannoís bronze leaves were placed on the central door, which were later destroyed by the devastating fire of 1595. Following the fire, the roof was replaced and three bronze doors were added to the façade and in the early 18th century, the inside walls of the cathedral was redecorated with large paintings.

The exterior of the cathedral is richly decorated with multicolored marble, mosaic and numerous bronze objects, which were placed on the eastern part of the roof in 1061.However, in the early 19th century, the original sculpture of the griffin was shifted to the museum and replaced with a copy. The facade of grey and white marble is decorated with coloured marble inserts. Above the three doorways are four levels of loggia divided by cornices with marble intarsia, in front of the single and double open windows. There are four open galleries above the door, with Madonna and the Child at the top and the four evangelists in the angles.

With the alternating layers of black and white marble and the elliptical dome inspired by the Moors, the inside of the Cathedral offers a spatial effect similar to that of the great mosques. The interior, subdivided at the front into a central nave, flanked by two side aisles, along with the transept and apse in the three naves, is covered with white and black marble and adorned with monolithic grey marble columns with Corinthian capitals. The inside of the dome, found at the crossing of the central nave and the transepts cross, is decorated with a rare painting in encaustic technique, depicting Virgin Mary in glory with the saints. The large mosaic in the apse, created by Cimabue in 1302 and depicting Christ enthroned between the Virgin and Saint John, was miraculously survived the fire of 1595.The pulpit, with its intricate architecture and complex sculptural decoration, depicts the episodes of the life of Christ, on its slightly curved panels.

Unfortunately, the cathedral, like the leaning bell tower, is sinking perceptibly into the ground, which is clearly evident from the difference in the floor levels of the original nave and the bays, which were added later.