Freeroaming Venice During the Glider Mission
https://youtu.be/0KHdwHy8-mk
During the glider mission (Carlo Grimaldi's assassination), leaving the Doge's palace results in mission failure. Well here's a way to avoid that. Go to the spot shown at 0:53 in the video and drop to hang close to the rail. This may take a few tries.
Leaving the place from the back is the only way so far to avoid desynch, although there is still a "no detection" rule during this mission.
You are now free to explore Venice with all the glider fires still there. One thing not shown in the video is there are some civilians running around saying things like "what is it?", and something about a "giant bat" (clearly reacting to the glider).
Oh great. 
Video accidentally deleted. Will have to re upload later.
EDIT: Fixed. What happened was i deleted the three videos that were edited together on the Youtube video editor, but later the videos were still there. So I deleted them again and the final video was deleted along with two of them. Didn't help that my internet keeps freezing on me.
Usually there isn't much to see on a freeroam. This one is cool because you could stand in the fires. I'm impressed with how thoroughly the fire pits are modeled. The base is an object with collision detection that you can jump onto (but not climb) and the flames themselves envelop Ezio in a convincing way. It would have been easy to skimp on these elements.