Egypt - Obelisk of Khamoon (part 4)
Tomb Raider Anniversary - Visual Walkthrough
When you are done with the mummies, flip the switch on the left side.
Then pull the box on the other side. You'll use it to reach the ledge above.
Grapple across and make sure you jump as soon as you land on the scarab.
The next section is basically a harder version of the jumping part you've done so far since it also includes blades. You'll need to jump as soon as you see the blade getting inside.
Next use the grapple, get to the other side, then turn around and jump to the ledge you couldn't reach with a normal jump.
Jump to the ledge across and then grapple to the other side.
In the end you should get to safety. This IS a hard part so don't get discouraged if you don't make from the first time.
Head through the corridor on the right.
You'll get back to the obelisk, but still have to lower one more bridge.