After you complete the Louvre Storm Drain you will use a hallway that leads all the way up. On your way there, you will notice a door that Lara not strong enough to open. Continue going up until you reach the final door. Upon entering that door, you will see security lasers. If you step into them, a policeman will try to kill you and both doors will be barred. If you make a mistake, return to the entrance and press [Action] on the wall to the left. Climb up onto the first little glass case, turn right, and grab the ledge of that hanging "box". Next, go to the end of that hanging "box" and do a running jump to the tall glass display. You must land directly on it; if you try to jump and grab the edge, the doors will bar again. Then, jump to the glass case that is to the right of the one that you landed on. From there, time your jump to the next case. You must now walk to the edge of the case you landed on. Grab the edge and shimmy across it, then turn the corner and land. There will now be two tall glass cases with a checkerboard laser net. Go to the glass case on your right. Jump up to grab the ledge, shimmy across it, land, and open the door. You will now see a room armed with a laser, and a policeman with a white shirt. Deliberately step into the laser and start shooting the cops. The one with the white shirt drops a card that you need. Next, go all the way to the back hall and pick up the medipack and press [Action] near the sign. Lara will say something. The door by the medi-pack is where you will come out of later. Go back to where you shot the white-shirted cop and enter the door. There will be another cop in the room. While armed, run into the room and kill the cop. You will see a portrait of Mona Lisa barred with laser in this room. Go to the end of the room and pull the small glass case away from the place it resides. Now that Lara is stronger, go to the glass case in the middle. Push it towards the painting of Mona Lisa until it stops on the stools. Next, go to where the small glass case used to be. You will see a card swipe. Press [Action], then run to the glass case in front of Mona Lisa. Climb the back and do a running jump. Press [Action] and grab the ledge over the painting and enter the vent. After you take these vents, you will get to the rooftops (where you get left off).