On June 24th. On that day the whole town celebrates San Giovanni, or Saint John, the patron saint of the city.
St. John’s celebrations end with the traditional fireworks display, the renowned fuochi di San Giovanni, that usually set off from Piazzale Michelangelo and draw huge crowds from both Florence and surroundings.
Most of the people usually gather on the Lungarni (the Arno river promenades). The best spots from where to watch are Ponte Santa Trinità, Ponte alla Carraia, or Piazza Poggi.