The cloister behind the cathedral in Prato.
Prato is a short train ride away from Florence, and we have made several visits there, including a rather strenuous tour of the Uffizi gallery yesterday, which was fairly astonishing: Leonardo da Vinci, Michelangelo, Botticelli.... Perhaps the highlight for me so far was our trip to Siena, but shortly we're off to Venice for several days to visit the Venice Biennale. All this is very exciting, and will take a long time to assimilate.
I've been looking out for things relating to Renaissance science, and was interested to discover that in Florence both the Duomo and Santa Maria Novella have inbuilt astronomical instruments in the form of a small hole high up in the structure to let in a ray of sunlight, and markings on the floor of the church. Among other things they were used to determine the length of the year precisely. I bought a small book explaining all this, but unfortunately it's in Italian.
The circle of sunlight on the floor of the Duomo in Florence. It is supposed to coincide with the marble circle at noon on the summer solstice - this photograph was taken a week before the solstice.