The construction of the Cathedral of Pavia was an extremely long process, spanning out over four centuries.

Its history dates back to 1488, when its construction began; from this date onwards many people contributed to the design of the cathedral, including Leonardo Da Vinci who visited Pavia during the early stages of the cathedral's construction. The church was not fully completed until the 1930s, more than 400 years after the first stone was laid.

The plan of the Pavia Cathedral is a Greek cross, with three naves flanked by semi-circular chapels. The central nave is twice as wide as those on the side; it is about 30 metres high and divided by two galleries. The centredome has an octagonal plan and is the fourth largest in Italy (97 metres high with a span of 34 metres).

The remains of St. Siro are conserved in the crypt of the Pavia Cathedral, the first bishop and patron saint of the city of Pavia celebrated on 9 December. The church also contains many other relics and remains of saints and beati, and perhaps most importantly, a precious silver and crystal 17th-century reliquary with the Holy Thorns of the Crown of Christ.