Climbing up to the Wall

At the beginning run into the open. Swim through the pool on the right. Swim to the opening on the left. Climb up onto the block. (In case you slide down later on, shoot the tiger.) Follow the way to the ledge. Jump to the column on the left. Jump once more to reach the next pathway. Follow it to the left. Climb up on the block. Turn around, making a 180 degrees roll. Make a running jump to reach a higher ledge. (From here you can shoot a second tiger down in the cave.)
Climb up the steps on the left side till you reach the wall. Turn to the left and make a running jump to get to the next ledge.

The 1st Key

Turn to the right and climb into the window. In the right corner is a trapdoor where Lara should drop down. After leaving the water climb up onto the highest block in the room. Make a running jump to the little alcove where the switch is. Grab the ledge and pull yourself up. Use the switch. Now leave the room through the open door.

On the Wall

Draw the weapons and shoot the three crows. On the right is a big opening. Slide down into the water. Dive into the underwater tunnel and pick up the Guardhouse Key. Swim to the surface and leave the pool. Draw the weapons and kill the tiger. (Shotgun! If necessary jump back into the pool or climb up onto the blocks in the corner.) After that climb up where the green blocks are. Back on the great wall open the door with the key. Again draw weapons and kill the nasty spiders. Climb up the ladder and kill another spider. (If you want to kill the spider before you climb up, follow the stairs and climb into the window. Kill the spider from there.)

The 2nd Key

Pick up the Rusty Key in one corner. Climb down again and use the key to open the next door. Follow the path. Beware of more spiders. On the right next to the skeleton is a large medipack and some shotgun shells. Pull the block at the end of the room out of the opening. Then slide down behind it. Jump into the water and walk straight to the left wall. Jump up and grab the ledge. Shimmy to the right. At the end drop into the water. Dive carefully to the right. Climb out of the water. (Save early, save often.)

Spiked Traps

Run over the collapsing floor. At the end, while running, turn to the right. (Don't let the boulders distracted you. Stay close to the left hand wall.) Run into the gap. Jump over the spikes. In the room underneath make a somersault to the left. Pick up the automatic ammo. Run to the wall and climb up into the hole. I recommend to save here. Follow the path. Since the floor tiles will collapse, don't stop running. Jump over the blades. At the end run to the left.

Secret 2:
Pick up the Jade Dragon.

Follow the next path on the right wall. Slide down at the end. Jump backwards, make a somersault to the left and drop through the collapsing floor. Again, I recommend to save.

The Slide

Carefully go to the small medipack and pick it up. Pass the two rolling blades as soon as they are past. Draw weapons to kill some more spiders.

Secret 3: Where the slide is turn around and hang from the ledge. Shimmy to the left. Let go of the ledge. Jump up and grab another ledge. Shimmy to the right. Climb up into the opening. Pick up the flares. On the left is a ladder. Use it to climb down. Run into the open. Draw weapons and go carefully to the right. A T-Rex is waiting for you. Start shooting and jump backwards. If necessary retreat into the doorway. After he is finished run through the valley. Follow the path and pick up the Golden Dragon. If you have found all 3 secrets, you will get the Grenade Launcher here. Outside there is a second T-Rex waiting. Kill him while still in the doorway. Run back through the valley into the opening. Turn around at the end. Go to the edge of the step, jump up and grab the ladder. Climb up to get back to the slide.

Use the slide to get down to the other side. If Lara reaches solid ground let go. Kill the two tigers. Run into the pathway on the right and to the big door ahead.