I could say that Firenze is the most impressive city I have visited Italy this time.
As far as I know, the city itself is UNESCO world heritage sight which means quite traditional and organised and obviously exquisite. Duomo which is a symbol of the city locates in the centre. Although the city is very small which is easy to walk around, the Duomo is so big. Its inside is absolutely magnificent. You might loose your words. Paintings on the whole of the wall helps me to understand the importance of this architecture. There were many tourists and also Christians.
And interestingly, I saw many people using bicycles. They are quite common and could mean the size of the city. Certainly, the central city is so small and very dense. And one of the characteristics of the city is the colours of flats. Orange or yellow, or in the middle, which is uncommon colour in Japan of course. And then typically the flats have window frames coloured brown or green. This combination looks super appropriate.
Firenze is quite famous for museums. There are two remarkable museums, one is Uffizzi and the other is Galleria dell'Academia. Davide by Michelangelo and Primavera Botticelli are famous. It is quite expensive to enter these museums but is still worth looking. Unfortunately photographing is forbbiden completely.