The Cathedral of Santa Maria is the symbol of the splendour of the Anagni and its history intertwines much with the sacred. It was built on the ancient pre-Roman acropolis, where there was a temple dedicated to Ceres and an ancient mithraeum that can still be visited in the basement and which is called the Oratory of St. Thomas Becket.

Its construction is due to the efforts of the bishop Peter of the Lombard princes of Salerno, on the spot indicated by San Magno who appeared to him in a dream and asked him to build a church dedicated to Our Lady and that he would find the necessary funds in Constantinople. In fact, when he arrived in Turkey he met the emperor Michael VII, thanks to the vision of San Magno, who financed the completion of the church.

The facade of the church is in sandstone, the local stone, in Romanesque style just as the bell tower which is separately located in the square in front of the main entrance of the church. The bell tower reaches 30 meters in height and has 5 levels of openings with single lancet windows, mullioned windows and triple lancet windows.

The sides of the church are equally interesting with the Loggia delle Benedizioni with the marble statue of Boniface VIII, seated on a throne set in a shell and inserted in a sort of canopy, which dominates Piazza Innocenzo III. The back of the cathedral has an even greater charm with the staircase around the three apses of which the central is finely decorated by a loggia with arches and columns.

The three front doors have three lunettes in the three naves. The central one has a Byzantine decoration and a head of a wolf and an ox that recall a legend. It is said that Bishop Peter performed the miracle of convincing a wolf to tow the cart with the stones along with the ox to help the construction of the cathedral. The interior has Gothic arches and a splendid Cosmatesque floor, which is made by the famous family of Roman marble masons.

In the central apse is the throne of the bishop made by the bishop Landone around 1262 while the balustrade that separates the area is recent and dates back to the twentieth century. The cathedral has a chapel on the right side dedicated to the Madonna della Misericordia while on the right side there are three important chapels: the Lauri Chapel, the baptistery and the thirteenth century Cappella Caetani.

Inside the church there are a few 13th century frescoes while the real masterpiece of medieval art is in the crypt under the church, a totally frescoed environment with three naves with 12 columns, a vaulted roof and a cosmatesque floor.

It is called the ‘Sistine Chapel of the Middle Ages’ for the magnificence of the paintings and their state of conservation and for the meaning of the pictorial cycle. The crypt is dedicated to San Magno and a section of the frescoes is dedicated to the history of the saint, who is also the patron saint of Anagni.

The first section near the entrance is dedicated to the cycle of life with the 4 seasons of man and the 4 elements, but also it contains the twelve signs of the zodiac and a correlation between microcosm and macrocosm.

Another section is dedicated to the philosophy of Plato and the doctor Galeno while a great cycle tells the ancient testament until the apocalypse. All the frescoes were made between the beginning of the 12th century and the middle of the 13th century by three different artists’ workshops.

A side aisle leads to the cloister with a lapidary and a cistern. In a building connected to the cathedral is the Treasury Museum which houses religious objects, sacred vestments and a rare reliquary set of Thomas Becket decorated with Limogés enamels.