Follow the path away from the lighthouse down the canyon wall. Kill the Turelim Vampire guarding the first cave on your left. Use one of the pipe staves on the wall. Enter the cave and go through the door. Follow the tunnel ahead.
Machinery fills the room ahead.
Watch out for the Turelim Vampire lurking there. Turn right and follow the wall around to find a crank. Crouch-jump onto the machinery in the center of the room. Jump up again to reach the top of the machinery. Walk to the block at the end of the machinery and shove it over the edge.