June 24 in Florence is always packed with events of all types that run throughout the day: flag throwers’ shows, a historic parade, rowers’ competitions along the Arno and fireworks (called “fochi” locally).
The annual fest coincides with the finals of the Calcio Storico in Piazza Santa Croce. The fireworks display lights up the skies above Florence from 10pm on. The best place to see them is the Santa Trinita bridge and the Ponte Vecchio.
Saint John was chosen as Florence's patron saint after the entire city converted to Christianity. Before this, the protector of the city was the God of Mars, whose statue used to adorn one side of Ponte Vecchio; it remained there until 1333, the year in which a flood in the Arno destroyed it.
It was, however, only until the period of Lombard domination (from the 6th century to the 8th century) that Saint John the Baptist was chosen as the city's patron saint because he was already the protector of the Longobard people. It was in this period that the Baptistry of St. John was built in Florence (circa 6th-7th century). According to legend, the baptistery was built atop the ruins of a temple dedicated to Mars.
The choice of Saint John as patron saint was primarily due to the clarity and brevity of his teachings, but also to his courageous and “fighter” personality.
The festival has been held every year on June 24 in San Giovanni's honour since the 13th century. It is also thanks to these festivals that the Baptistery of St. John and the Duomo of Florence became important places in the religious and political life of the city. Festivities took place, in fact, right in front of the baptistery. In the early years, celebrations concluded with the parade of a wax St. John on a cart that was taken from Piazza Signoria to the Baptistery; the cart then exploded with fireworks, giving way over the years to what became known as the traditional Scoppio del Carro. Later, however, this ritual began taking place only during Easter rites, and no longer as a celebration of Florence’s patron.