Collapsing Floor

You'll slide down to the ground. Run into the passage. Continue along the path till you come to the high passage with the stone floor. Run into the passage. (In the video you can see the floor crumbling.) Run forward and jump to land on safe ground. (The door in the next room is locked, but you can see a lion in the chamber underneath.) Now hang from the last ledge. Shimmy left. Crawl into the gap. Turn around and lower yourself backwards into the tunnel. Press the button there. Climb back into the gap and shimmy back into the big room. Enter the next tunnel and slide down at the end.

Gemstone Piece

While still sliding get your shotgun out. Shoot the lion you'll meet downstairs. Three shots will suffice and he won't have reached you by then. Press the button. Turn around quickly, get your shotgun out and shoot the second lion as well. Enter the next room. Climb up the ladder. Collect the gemstone piece from the pedestal in this chamber. Now step outside.

Gladiators and Door Buttons

Turn left and shoot the gladiator. (2 shots with the shotgun.) Enter the tunnel on the left and collect the small medipack. Now head up the ramp on the right. Shoot the next gladiator coming from the left. Step into the passage he came out of. Collect the Uzi ammo and press the button. (This will open a door at the top.) Run up two more ramps to get to the top level. Shoot the gladiator there as well as the lion. Step inside the chamber and follow the passage to find another chamber with a pair of Uzis.

Timed Chain Riddle

Now run down the ramp again and enter the big cave on the right. (You'll come to a bridge with a big platform in the middle. Opposite is a close door. In the middle of the platform you can see an artefact lowered into the floor. On the left you can see a lower platform with a rope and on the left is a higher platform.) Carefully drop down into the cave. Climb onto the platform with the rope. Pull the rope three times. (After the second time you can see the result from where you are. You've elevated a pillar with the artefact.) Now you have to be quick. Make a sideflip to the right. You might slide a bit. Quickly turn to run down the stairs and from there jump onto the thin platform. Make a running jump onto the two steps ahead. From the end of that block you have to do another running jump. (You don't have the time to position Lara, so just press jump when you've reached the end. You have to time it right.) Grab the ledge. Pull yourself up. Make a roll and a flip to the right. Turn a bit to the right and run forward onto the long ramp. Again make a running jump to get over to the huge platform in the middle. Grab the ledge and pull yourself up. Quickly step towards the column and press action to grab the gemstone piece before it can vanish again.

The Fall

Now turn right and head towards the close door. It will now open if approached. Run ahead. The second door will close again and you will drop through a trapdoor. (Watch the movie: Lara slides. She can grab the ledge before she drops down. Pierre will appear. He will help Lara up. Now he is between Lara and the edge. Lara steps forward he steps back and drops down.) Now walk through the door on the right.

Gemstone

Combine the two gemstone pieces and use them at the slot. (The gemstone will turn and the floor will start to collaps.) Stay where you are and keep pressing forward and action just in case. You'll then land in a niche underneath the platform. (Picture 1) Hang from the ledge. Shimmy around to the left, around the corner and to the end. At the end you can let go to land into the passage opposite safely.(Alternatively make a roll. Run forward and jump over to the platform on the right. Press forward to get close to the wall. When dropping down Lara will land on the ledge underneath.

The Key and the Statue

Enter the next room and step onto the block. Picture 2 Climb up. Take out your shotgun and shoot the gladiator and the lion quickly. Collect the key the gladiator loses. Approach the big gate and use the key to open it. Behind the door a statue with a hammer will come to life. Like the statue in Trajan's Markets he will shoot green bolts at you. Take the best weapon you've got to bring him down. Start with the Uzi if possible.

Philosophers Stone

Climb into the chamber that opened and collect the key on the pedestal. Get back out and open the door on the left with it. Slide down the slope. You'll land on the platform with the Philosopher's Stone. Now take the Philosopher's Stone to finish this part of the game.