Two Birds, One Blade

Head to the viewpoint marked by a yellow marker and climb to the top. If you haven't climbed it before, look for ridges on the south side to reach the very top, then climb the cross for a scene.

After a scene with Bartolomeo fighting Dante, dive off the cross into the canal water and make your way to the battle.

Help Bartolomeo by defeating the Brutes and other enemies. Watch Bartolomeo's health, though it should not be a major issue.

Proceed north where another fight erupts. Defeat or ignore the normal enemies.

Engage Dante. You cannot disarm him, even when he is weak. Counter and dodge until he flees.

Chase Dante and his companion. Try to find a route to the rooftops early on.

You may be able to double air assassinate both of them if you move quickly.

If they reach a boat, climb the crane overlooking it to attempt a double air assassinate.

If the double air assassinate is not possible, wait for them to split up and assassinate Silvio.

Dante will approach; counter-attack to kill him in one blow.

This concludes Sequence 10 and begins Sequence 11.

Walk with Leonardo and listen to his conversation with Ezio, which leads to a startling conclusion.

The north section of Venice is now open. Find and synchronize the first viewpoint in northern Venice.

Synchronizing this viewpoint reveals a Codex Page to the east.

Proceed to the next mission marker.