Built at the end of the 11th century, the narthex is a dimly lit vestibule ‒ a transitional space serving as a passageway to three important areas: the church, the Chapel of St. Michael above it and, in earlier times, the cloister, whose door is now bricked up.
The vaulting in the aisle on the southern side of the narthex features several paintings depicting Adam and Eve being banished from the Garden of Eden, and salvation through the Resurrection of Christ and the Last Judgement. Francis of Assisi can also be seen, talking to the birds. The head of Christ right in the middle reminds viewers that he is the centre of the universe.
These images were a means of passing on the Christian teachings to the faithful, most of whom were illiterate.