Need help Please

Im playing AC revelations and i am in some kind off tombe i think it has to do with the keys you have to find, how ever i have crossed the tombe all ready 3 times and every time i get in the end chamber there is a box which lights up with hawk eye how ever if i standin front of the box it does'nt give any options of interaction ore something like that. It is the tombe which is at the big wall and where you have to climb on the jail cell in kind of the end. Im a doing something wrong ore what should i do? i cant get out of the tombe before i have made any actions. Can someone help?