Florence is a highly interactive city with many things to do and see. Below is an outline of when things are open and where they are located. I won't attempt to list every possible activity, but instead just highlight the main sights and some of the more complicated ones to visit.
Yes, Siena is what I would describe as "Peak Europe." It doesn't get better than this. You can think of Siena as a smaller and more subdued version of Florence. Florence overflows with tourists, who crowd vast avenues lined with marble-clad palaces. In contrast, Siena awaits a smaller crowd meandering through alleyways of sun-baked brick.