The last simple quest will be waiting for you at the stables . Groom will ask you to find your uncle's horse .
Animal is marked on the map. Get close to him , press B and go to the stable .
After dealing with all tasks go to the palace , when you will be able to attend an important meeting .
After the cut scene, go upstairs  and open the door leading to the bed room (B) .
You will meet Catharina here. After the night  the town will be attacked by Borgia's army .
Your horse will ride alone until one of the building will collapse . Ezio will jump on the wooden beam .
Press RT and A to jump on the other buildings . Few moments later, you will find yourself near the building with the ladder .
When you will be there, a cannon bullet with fly near your character . Use the hole in the wall to go upstairs and then turn left .
At the end, you will find a cannon . Use it to destroy cannons located on the left .
After dealing with them, try to eliminate enemies located on the right . After some time, one of your mates will be shoot. Get close to his cannon and destroy last enemy units .
When you will do this, the second part of the siege will start. Enemy soldiers will start to attack your town . Go there and get close to the wooden pole located near the tower . As a matter of fact, you will be transported above.
Jump down on the other side  and then kill all enemies using your counterattacks .
At one moment, a knight in the plate armor will appear . Dodge his attacks with RT and attacks with A. After successful dodge release RT, attack him with A and X. Counter attacks are very useful here. Remember that you can change your weapons with D-pad .
Your character will be wounded but he still can fight. Defeat more enemies  and go to the villa  that is marked on the map.
When you will be upstairs, you will see your sister who will be fighting with some soldiers. Help her (you must be very quick to save her) .
Fallow Claudia and you will get close to the building . Hold RB and choose the gun icon. Kill two nearest enemies .
Target them with X and then shoot by releasing this button . After the fight follow your sister and enter the building .
When you will be inside the corridor go straight ahead  until you will get to the glowing point . You will see a longer cut scene now and after the film you will return to the Desmond body.