Dig SiteStep through the gate. On the left you will find nothing, so turn to the right. In the first trailer is a guard. He will notice you and come out when you approach. You can use the K2 Impactor to take him out. He has more Ammo for you. Inside the trailer you can find a switch, which will turn on the power elsewhere. Now run towards the tent where the next guy is waiting. He loses a Weapon. Through the metal gate between the tent and the first trailer you will come to a separate chamber. The switch in the first trailer has activated the generator here.
ScannerEnter the chamber. At the desk you will find the controls for a scanner. Use it to search the ground. If you move it to the back and a bit to the left you will find something. A symbol. The computer will mark the spot and print a copy. Step a bit to the left and take the First Ancient Symbol Copy from the printer. Now leave the chamber again.
Second SymbolNow enter the second trailer. Here you will find the Second Ancient Symbol Copy in the printer. Collect it. At the computer further on the left you can gather some information on the Nephilim. If you step outside a third guard may appear. You have to get rid of him as well.
ExcavationNow advance towards the pit. If you run back to the left you will come to a ladder leading down. Climb down. Run along the scaffold to find the next ladder you also climb down. Follow the walkway to the end, past the ladder leading up, and jump over the gap onto the next part. Walk over the scaffold till you come to the next ladder. Climb further down. Look down to see a guard. Shoot him from up here. Run to the end to find the ladder leading down. There is supposed to be a board down here - see picture - which tells you the two symbols you will need along with the ones you have collected. DaPete has found this board, but when we went looking for it we couldn't find it anymore. Maybe you are lucky to find it. If so please send me a savegame. (PC users)
On the bridgeClimb up the ladder between the two barrows. Here you will find a climbable wall. Climb up and to the left till you have safe ground under your feet once more. If you are having trouble getting around the bends press up and left/right at once to climb diagonally. At the platform at the end you will find a fence blocking your way towards the clock. Look up you will note that you can climb at the underside of the bridge. Jump up and climb to the other side. You will barely have enough time so don't stop. On the other side you can climb up onto a wooden platform. From here climb up onto the bridge.
First time I did so I encountered a bug where Lara would skip to the next level.
If that doesn't work, you might have found another bug. I have encountered a bug here where the power would be turned off and all my symbols were gone from the inventory.
Mystique ClockRun back across the bridge and climb back down. From the rock underneath the bridge take a running jump towards the lift. You will now come to a clock you have to set. There are four cogs and a lever on this clock. If you use the lever, you will turn the four cogs, one clockwise, the other one counterclockwise. Around the corner you will find four levers, one for each wheel. By using one lever you will lock the according wheel.
Look into Werner's Diary. You will see that he has found two symbols already. The first and the last. See picture. You have found two more symbols earlier on. Together they form the right combination, which you have to enter. Start by using the lever at the clock till the first symbol has reached it's place. Then go around the corner and lock this wheel. Then return to the clock and turn it till the next symbol has reached it's place. Lock it again. Repeat this till you have entered the right combination. This will open the gate above you.