Uli KeyRun towards the door ahead. It opens. In the right corner you can find a door with a lock. On the left is a chamber with a couple of buttons overhead. Run over to the right and up the ramp there. Climb up the ladder in the corner. Follow the passage. After you went down you will find a lever on the right. Use it. (The left passage will only lead to a closed gate.)
Run along the dark passage and step into the window on the left. Take a step back and make a standing jump onto the pillar in front of the window. Turn right and take a running jump towards the platform with the crystal. Collect the crystal and the rocket. Drop to the ground.
The Five SwitchesEnter the passage and climb up the ladder. At the top you will come towards the gate in the passage from the other side. (The lever on the right opens the gate.) Step out through the window on the left. Run towards the left end of the balcony and pull the lever. (The camera shows you the room with five switches.) Get back inside and slide down the ramp. At the end you can find another switch. (You can now see a ladder in the room with the five switches.) The big gate has opened. Step outside and run over to the other side. Climb up the ladder. You have to use the first, the second and the fifth switch. (There is a reason why you have to use exactly these three buttons, there are two reasons to be exact. Harald has given me one solution. At the lever where you have been before, also see picture above, is a noticeable wall texture. In it is a three-digit number. 1 - 2 - 5. Aha! Take a look at the picture on the right for confirmation. Click it for a full size version. The second solution is more scientifically explanation and comes from Dimitri. Take a look at the five switches. Also see the picture on the right. At three of the switches, you can find a food chain. 1: Man-> Animal-> Plant 2: Man-> Bird-> Fish; 5: Man-> Bird-> Plant. In the other two cases, it's not correct. Plant eats Animal or Fish eats Bird doesn't make any sense.)
The BridgeStep through the open gate. Run out onto the bridge. Out here you will be attacked by dragonflies, which appear in regular intervals out of the wall on the right. Run towards the gap in the bridge and make a running jump towards the platform with the crystal on the left. Grab the ledge and pull up. Collect the crystal. Turn towards the chasm and climb up to the right. Look up. There is another platform overhead. Walk towards the edge. Jump straight up and pull up. Turn to face the pillar of the bridge. Take a running jump to get there. Grab the ledge and pull up.
Stand on the right end. In the middle between the bridge here and the part opposite is an invisible platform. Wait for one of the dragonflies to come to this area. Then kill it quickly. It might light up the platform for you. (First Picture.) I found it very difficult to light it up with other means, but you can try using grenades or flares. Jump onto that platform, a running jump is necessary. From there jump onto the left pillar of the other bridge part. Wait for the next dragonfly to come out and kill it. There is another invisible platform which might be lit. Second Picture. Jump onto it. From there jump into the nest. Collect the small medipack and some ammo for grenade launcher and desert eagle ammo. Avoid the pit. Return the way you came.
Passage next to entrance - MudStep through the passage on the right, next to the stairs. The gate closes behind you. The gate on the left stays closed. Wade through the mud. Follow the path to the right. A couple of dragonflies will appear, you might have to get rid of them while in the mud. After a long walk you can climb out to the right.
Secret 2 Preparation (Possibility 1):
After climbing out of the mud turn around. Take a standing jump onto the slightly sloped block on the left. From there take a standing jump across to the other side, where there is a triangle platform. Turn to the left. You can see an entrance right underneath the bridge. Take a running jump onto the block underneath. Climb up into the opening. Drop down and pull the lever. A block in some room will drop. Collect the small medipack and climb back out. Turn right and make a running jump towards the little triangle of the rocks in the middle. From there jump back towards the passage leading up to the bridge. Run up again.
Secret 2 Preparation (Possibility 2):
Cross the bridge. On the other side there is an opening right underneath the bridge. Stand with your back to the left ledge. Jump back and press action. Let go of action before Lara can grab the ledge. She will land on the platform underneath. In the picture you can see the part of the bridge where the opening is. The arrow indicates the opening. You have to stand on the ledge you can see in the middle, in front of the entrance, with your back towards the left. (Click to see larger pic!) From there climb into the opening. Drop down and pull the lever. A block in some room will drop. Collect the small medipack and climb back out. Turn right and make a running jump towards the little triangle of the rocks in the middle. From there jump towards the passage leading up to the bridge. Run up again.
Passage on the right - WaterThis time choose the passage on the right. You will come to a chamber with water below. There are some blades. Jump into the water past the blades. Dive into the pit at the bottom. Follow the passage to a chamber with another blade set in front of four passages. Dive into the left passage. Catch some breath and then pull the lever. Dive back out. Dive into the right passage. Hurry the door there is timed. Dive up the long shaft and catch some breath. Dive over to the desert eagle ammo and collect it. Mind the blade set. Turn around and dive towards the uzi ammo and collect it as well. Careful there is another blade set. Behind the next blade in the right niche you can find a lever. Use it. Dive down and into the now open passage. Climb out. Collect the next Oceanic Mask. Then collect the crystal and pull the lever. Dive back towards the blades. Dive into the lowest passage in the wall opposite. Follow the shaft down and use the lever on the left. Dive into the gap and down to the right. Pick up the MP5 Ammo. You will now come back to the first blade set with niches. Dive into the lowest passage and follow it to the right through the open door. Catch some breath and follow the next water tunnel. Dive up the long shaft. Climb out and pull the lever to drop through the trapdoor. Follow the passage and step through the opening gate again to return to the beam. Climb up the stairs again.
Passage on the Left - MazeThe next part can be solved in many different ways. I have chosen the shortest. Take a look at the map when you are lost.
Turn left and into the first passage on the right. Follow the bend on the right. Turn left and left again to find some Uzi Ammo. Get back out and turn left. Then turn right. Turn left again and again. Turn right and kill the dragon fly. Push the crate into the wall. On the left you can find some flares and a small medipack. Run back down and turn left. Run to the end and turn left again. Turn right and get into the corner. There you can find some shotgun shells. Turn left then left again and follow the passage back down to the entrance.
Turn right. Then turn left at the first opportunity. Follow the path to a small medipack. Get back out and turn right to get back onto the path you were on.