Coastal Thailand - Bhogavati
Tomb Raider Underworld - Visual Walkthrough
Continue forward, balancing, jumping, and so on.
Here we are.
Grapple and pull down that grapple-point/horizontal pillar.
Get down.
Go on the opposite wall from where you came down and grapple up.
Put the cage near the balancing statue.
Then go up the stairs, and climb on its hand.
It will go down and also pull down the giant statue's hand.
Go down fast, and put the cage under its scale (see image below).
Go to the lowered arm and put the stone.
Kill some more lizards, and get on the other side.
Jump on the scale of the other statue which does not have a timer. Put the stone on the other arm.
Next you just need to drop down and position the two statues in the places marked by the light. Make sure the mirrors are facing OUTSIDE the ring - use the middle path to switch their positions if you need.
When they are both in the right position the middle diamond will shine and a secret entrance will open below Shiva.
Head through the newly opened entrance and you're off to the next level.