The construction of the cathedral began in 1107, but the works were damaged and the building process stopped after the earthquake in 1117.

In 1129 the construction resumed and most of the building was probably completed around 1170. Then many alterations and modifications of the building started. The façade was probably built in the late 13th century.

The massive tower is named "Torrazzo". With a height of 112.7 metres this tower is one of the tallest brickwork towers in the world. It is the oldest brick structure taller than 100 m that is still standing.

The construction of the tower began in the 1230s. It was completed in 1309.
The astronomical clock, built in the 1580s, is still the largest - worldwide.