Terrace overlooking the river Arno
The best views of Florence you can see from the Piazzale Michelangelo and the nearby church of Santa Maria a Monte. In the summer months you can visit Forte Belvedere overlooking the city. A particular view of Florence is also the one that can be enjoyed from the hill of Fiesole, where there are monuments from the Roman and Etruscan. You also have a particular view from the dome of the Duomo and Giotto's bell tower (to avoid the queues you have to bookwell in advance).
