To get to the top of the pyramid in the underground temple in Hunter’s Moon in Shadow of the Tomb Raider use a rope arrow to clear the gate and push the cart through the gate. Climb the stairs to the left and jump across to the bell counterweight. Use the other bell counterweight to get to the other side and follow the passage. Use a rope arrow to get across to the next corridor. Go down the corridor and jump across to the bell counterweight and then to the rough stone. Go up to the cart on the right and push it down. Use the pulley to turn the cart so that you have the rope wrapped wooden beam facing you. Attach a rope arrow to the rope wrapped beam and use the pulley to pull the cart up and release the cart.
Use the platform on the right to jump up to the bell counterweight and then quickly jump across to the ladder. Make your way to above the pyramid and use the rough stone to repell to the top of the pyramid. .
As found on Youtube