Borgia tower
Borgia towers are large towers set up by the Borgia in Rome, used to spread their influence throughout the city. Ezio Auditore da Firenze has to kill each tower's Captain, and burn the towers down. To escape the collapsing structure, he can perform a Leap of Faith, in the same manner as with view points.[1] Before destroying each tower, Ezio has to assassinate its Borgia Captain, as they control the towers. There are twelve towers in total so far. Each Captain can act differently when they spot him; wherein some might flee, while others choose to fight. If Ezio lets the Borgia Captain escape, he will have to wait a full 12 in-game hours for the Captain to re-group with his guards to reattempt killing him. With each tower blown up, the Borgias' influence decreases in that particular district, which also provides its populace the opportunity to start shops and allows Ezio to recruit one more assassin into the order. Crime will decrease, as bandits will start to leave and the number of guards in that area will decrease as well.[2]The map on the pause menu identifies the towers with a small castle icon, unlike the view points, which are marked with an eagle. To enter a Borgia Tower, Ezio will sometimes need to find and access it using a secret entrance.[3]
Once Ezio has destroyed a Borgia Tower, it will function as an Assassins Tower, which has the same use as an Assassins Pigeon Cage
Captains
Centro District
Antico District
Campagna District
Walkthroughs
Eventually, Machiavelli stops as Ezio takes it upon himself to kill a Borgia guard that's blocking the stables. The guard is inside a small building within the larger stables compound, and there's no way to get to him without stirring up attention. So you might as well not bother trying to be stealthy. Rush into the stables compound and move toward the red marker that points of the captain's location. 
You can fight off the lesser enemies around the Borgia captain no problem and without any particular goal in mind. Just kill 'em. However, if you want full synchronization you'll need to kill the captain by throwing him into the nearby scaffolding. Thankfully, it's pretty easy to execute, though we suggest killing off the lesser enemies first to make it easier still. Grab the Borgia captain toss him toward the scaffolding. Aiming is difficult, though the Left Analog Stick will help. Tossing the captain into the scaffolding results in instant death. Return to Machiavelli afterward. 
Finally, you need to burn down the stables tower to properly rid it of Borgia influence. We suggest entering the stables by climbing to the top of it—no need for unwanted attention—and from there you can climb a ladder at the south side of the tower. Make your way to the top of the tower and press a button to end the mission.
tower 2
this tower you can see during the mission HIGH STAKES NEGOTIATION
shoot the borgia captain with your hidden gun and climb the tower