Small medieval town on the top of the hill, hometown of Giovanni Boccaccio (the author of Decameron). Almost no tourists and no shops - authentic medieval atmosphere. There are some museums such as Boccaccio museum with a nice view from the top of the tower and palazzio pretorio with old frescoes, prisons and Etruscan museum.
You can walk the medieval streets as if you are in XIV century.. You can enjoy beautiful views from the hill over the valley.. you can see the church where Boccaccio was buried and many mistical stories happen.
Visit Certaldo Altonin June for the medieval dinner or July for the international street artists festival Mercantia. Amazing!