Now you should be back to the main room.
Do a running jump to the ledges to the left (same one you used to get there) and this time, head towards the statue.
You should get easily on top of the entrance with the grates. Shoot the ring that holds the huge shield in front of you and then use the grapple twice to get across to the second switch.
One more grating to go.
Now for the last one, you need to move the other platform as well (it was released when the shield felt down) and position them so you can get across on the right.
If at first you don't succed, try again. You don't have to position them perfectly, just so you can get across.
This part looks very much like the previous, dodge arrows, jump from ledge to ledge until you get to the final room.
And there you go ... pretty simple, right?
Well, no, because the floor collapse and you find yourself jumped by wolves. Hey, it was too good to be true.
Kill the wolves and then go to the dark section and in the middle you'll find a small cage. Pull it out and position it so you can reach the ledges nearby.
Climb as high as you can, then do a back jump. Lara should grab the pole hanging from the ceiling. Jump to the second pole and then to the ledge.
You'll need to do some more backjumps and swing on a thin pole, but in the end you'll get to the side with the switch.
Before you flip the switch, you can go for the artifact #2.
Jump to the ledge above it then drop down to pull the switch. And that was the final grating.
To get back up, jump to the pole to the right and then use the ledges in front of you.
Another dinosaur will come to greet you, finish him quickly and get back to the main room.
With all gratings cleared, head into the room.
And there is it: the first piece of the key (and yeah, a dead guy - which for some strange reason won't attack you).
A cutscene will follow and the whole tomb begins to cave in (now where did I hear about this part before?).
Anyway, head out since you pretty much finished this level.
At the exit another cutscene, this time a guy with a nice shotgun is waiting for you, I'm sure there's no problem for you though.
And that's all here folks, time to go to Greece.