Turn the levers so that they're all facing in to the small area between them all and a pool of water will open up. Once you've done so exit out the left side of the cavern and you'll come to a room with some statues.
Go inside, dispel the illusion, and you'll have a Golem to fight. If you head around to the west of the island and hug the outside of it as you head north you'll find a path that leads down to a cave. On Temple Island there is a hidden cave to the northwest of the island.
A bit more legwork for this collection of diagrams.
