Inside the Basilica of St. Petronio are also preserved four of the oldest symbols of Christian faith in Bologna: the four crosses. Legend has it that Sant’ Ambrosio placed them in ancient times on the four corners of the walls, as a symbolic shield of the city from external dangers.
The four crosses were named after: the Martyrs, the Saints, the Apostles and Evangelists and the Virgins. Before being moved into the church, they were in small chapels: one in Via Monte Grappa, one in Piazza Ravegnana, one at the crossroads between via Farini and via castiglione and one in via Barberia. They were rebuilt several times over the centuries, until 1798, when they were moved due to the urban changes that Napoleon was making. The transfer was particularly symbolic, because the crosses symbolized the passage from the Roman city to the free municipality, seat of the Studium, and bringing them to St. Petronio increased even more its value as a religious temple, but above all its civil value. Currently the crosses are located in the side aisles of the basilica, positioned in square on the original columns, to ideally recreate their embrace to the city.