Kill them (again) where they stand
http://www.youtube.com/watch?v=A7Nces5P3rw
You can breach the walls of l'Arsenale to assassinate Dante Moro and Silvio Barbarigo in ways that were not intended. While Bartolomeo and Dante fight outside of l'Arsenale, Silvio watches from the wall above. You can climb up to Silvio and kill him if you like (Thanks to runescaperox50 for the tip!), but the hidden gun and throwing knives don't work on him. You also won't be able to move his (talking) dead body, as he will teleport back to his original location when you put him down. The developers put Silvio on an invisible platform so that he can look over the wall. The invisible platform extends out into l'Arsenale for a bit, so you can "airwalk" if you like.
You can use this opportunity to play around. You can perform a "hole in one" to get down to ground level in l'Arsenale. Once inside, you can kill some guards so that you don't have to deal with them later.
Be sure to save Bartolomeo before he loses all his health. If you like, you can kill Dante by drowning him. Both Silvio and Dante will then be resurrected due to scripting of the game. Again, you can climb over the wall of l'Arsenale. This avoids the trigger of crossing the threshold of l'Arsenale. As a result, Silvio and Dante do not start running, and you can remain Anonymous upon entry.
