I like the Doge's Palace mostly for the architecture, not so much for the art collections. I very much enjoyed the SI tour, learned a lot about the history of Venice in her heyday. This is not a tour of the public spaces of the sight, but more like a back-door opportunity. The tour goes to the upper floors which are not otherwise accessible to the general public. Be forewarned: you will be under right the metal roof, no AC, no fans. If you go in summer, it will be hot. Take a folding fan and lots of cold water. I went in winter and it was bitterly cold, but all of us were grateful it wasn't July.