Go to any location that you can exit and re-enter easily with money or reusable items (health packs, bars, etc.) that can be picked up. Keep leaving and entering the screen. The money or item will still be there each time.
Go into the pawn shop after you talk to the women. After you talk to the man in the pawn shop, leave. Then, go straight until you get to a sewer drain cover and an object or item toward your left. Pick it up. It will be money. Go back to the pawn shop. Then, walk back out of the pawn shop. Return to the sewer top where you found the money. There will be money there once again. Continue doing this for unlimited money.
Instead of holding [Action] to fire, quickly tap it repeatedly. Lara will shoot the weapon much faster, making it easier to eliminate targets.
Stand directly in front of the cabinet and press [Crouch]. When the hand appears, press [Action]. If done correctly, Lara should reach through the door while crouched and grab a gas mask. This may also work in other places.
Turn on the disco lights that move up and down. Then, go up to the second level. there should be a box on the opposite side from the one that you came up from. Move that box and climb on top of it. From there you can climb up again. A huge catwalk will fall. Make a running jump and get to the other side. Next, jump onto the disco lights and enable the walk feature. Walk to your right, then turn again once you reach the the end of the frame. Jump and grab the edge. You must now climb the ladder. There should be a slide with a gap at the bottom. Slide down and jump to the other side. Then, turn left and make that jump. Straight ahead is a metal frame that you can jump to and grab. Shimmy across and pull yourself up. Walk to the edge of the wooden platform and jump to the next catwalk with a bridge. Kick the bridge down and break the door open. Go into the room and pull the left lever until the broken light is on the bottom left side of the square. Then, pull the right lever and you can collect the object. Go back across the bridge, then exit through the door that is in the room with the levers. Forget about the ladder in there, as all you get is a candy bar.
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).
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.
When you enter, you will have a few enemies. Run all the way to the end, and open the door to the room. Shoot the people inside and press [Action] on the gadget on the wall. Run out of the room and to your right until you see a small path to a large room with a computer. Look into the computer and search the ground (the second Ancient Sign is at the end of the plot), and print it. You now have two of the four Ancient Signs necessary to enter the Tomb Of Ancients. Now, climb down the ladders to the bottom of the archaeological dig and climb up the climbable wall. Drop down at the landing at the top. Look up, and you can monkey-bar across the bottom of the bridge above you. Be careful, as it is a long bridge and Lara's strength is limited. Climb up onto the bridge and go to the place that you saw during the intermission sequence when you pressed [Action] on the gadget in the room. Press [Action] on the door. This will lower the improvised elevator. Now, drop down to the ledge beneath the bridge. Jump to the improvised elevator landing and you will now see a giant wheel. Look all the way in the back of your notebook. It will show you the first and last Ancient Sign. The middle two are the ones that you collected from the printers in Carvier's office and the plot. Turn the wheel until you find the sign, and go up the stairs and turn the wheel to lock the sign in place. Once you have arranged the signs in order, the wheel will lock. Get back to the top of the bridge, and you will the see the circle on the ground has opened. You will fall into the next level, The Tomb of Ancients.
Engage the knights in close combat. Kick or punch them off a nearby ledge to get rid them for good.