When you are off the rooftops and into a small storage room, you will notice a hallway beyond the door of the storage room. You will see a door with a card swipe, Madame Carvier's office all the way at the end of the hall, and two doors on the side. Open both doors, kill all the cops, and take whatever you can. Now, go to the second door where you can look into the cameras. Find the one with Madame Carvier's room and zoom onto her computer. You will see the numbers to open her door. When you open her door, grab everything you can; one Ancient Sign is in her office. Then, go to the card swipe door and enter it. These halls will lead you to the Archaeological Dig.