Video walkthroughs for Assassin's Creed II from SuperCheats
Perform a Leap of Faith from the top of the Giottos Campanile in Florence to unlock this achievement or trophy, worth 10 gamerpoints or a Bronze trophy.
Giottos Campanile is the bell tower in the northeast corner of the San Giovanni district, which is accessible from Sequence 1. Climb to the very top of the tower and perform a Leap of Faith after synchronizing the Viewpoint (if you havent already done so).
See the video to learn how to get to the top.