Sequence 7 - By Leaps and Bounds
Rosa will challenge you now. You have to go to a nearby cathedral.  Speak with the girl. 
You must climb to the top of the tower. The easiest way to start near the place where you are standing - climb on the gate.  Then move to the right - there are small gaps in the wall, so you can use them to climb to the top. 
At the top, go to the tower.  Jump on it and climb up using your new technique. 
At the top enter the bright circle.  Jump down and talk to Rose. 
Sequence 7 - Breakout
To get the second mission you must go to a thief that is standing on the roof.  Ugo will ask you to release his friends. First, go to the north-west and watch the situation that is happening near the cage with prisoners. 
Soon, guards will go away - only two will remain. Then go down and land on the cage.  Murder a guard and free prisoners.  Obviously it will alarm other soldiers - fight with them.
Your new friends are very agile thieves, so you can immediately begin to climb - after a while they will follow you. One thing you have to avoid are archers. Soon you will be at the proper location.  Now you have to open a second cage - use similar tactic. 
With the second group of freed thieves you have to run on roofs to Ugo (eliminate one or two archers).  Leave prisoners at secure location. 
The third cage will be guarded by two guards.  You have to stand at the edge of the roof and perform spectacular, double murder. 
Free these thieves and go to Ugo.  You need to go to the docks for the next mission.