in's Creed 2 gamestop exclusive in-game level locations.?

Ok, i put in the codes for these levels, so that's not the problem. I was also able to play the Home Invasion level about midway through the game. Unfortunately, my lovely wife threw away my paper that shows the location of the other one. I remember reading about a bell tower, and the only one i can get into just has a treasure chest. Can anyone tell me where the second one is, and how to get in. Or if there is a certain time frame in the game in which i have to play it? I figured since i beat it and am just free roaming, it would let me get in. Thanks.