K so, I was on my way to what I thought was an Assassin recruit, and I had to open a door. When I did that I was in an abandoned prison-like thing. So I though, all right, lets just do this a be done with it. So I got all the way to this place with nothing but a bar-door, a whole in the ceiling, and no way to get out (this was after about an hour of climbing). So, after another 30 minutes of saying "what the shit do I do?" I replayed a DNA memory to see if it would put me back in the map.
Nope. It put me at the start of this place. I have no map, and no idea where the hell I am going. I found this place at the very left side of the map where there is a door that looks like it goes into the big wall that I believe surrounds Constantinople. I am not sure if this is a tomb that I stumbled across, or the hidden places. But I have no idea how to get out of here.
OMFG! So as I was trying to get back to the end with the door and the hole in the ceiling, I fall off this crate and die, just to be able to do it all over again. I don't even know where I am.
Edit: Found out I am in Vlad The Impaler's Prison. I watched a video and at the end with the room I am describing, you should be able to open a coffin and steal a sword. Only problem is it never gave me this option and now I have no idea how to get out.