For a memorable stay in an historic Florentine palace, Palazzo Uguccioni offers five vacation rental suites in Piazza della Signoria. All the apartments are on the top floor of the palace, thus avoiding the noise of the busy piazza and affording breathtaking views of the Palazzo Vecchio, Duomo, Bargello and Badia Fiorentina.
Palazzo Uguccioni is not a hotel or a tourist rental agency, but is a Florentine family who has restored part of a prominent building. From the website:
We are simply a Florentine family with a desire to create something original. In fact, we have refurbished these 5 magical apartments in the heart of our beautiful city. We now offer them to those who wish to experience the city center, as an open-air museum, to those who wish to be in close contact with art and history, and to those looking for a chance to discover parts of the city which have remained authentic and to savour those rare moments which have remained typically Florentine. In other words, to be able to step out from your door and discover all of Florence only mere footsteps away.
The palazzo itself has a famous Renaissance facade, dating back to 1550. Although the architect is believed to be Mariotto di Zanobi Folfi, the design is often attributed to Raphael. You can't get more historic than that...