Go through the fake wall on the right and enter the next room. You may think you've run into a dead end, but don't be fooled the Dungeon Map and the Lens of Truth reveal several hidden corridors. Play the Song of Storms and a fairy will appear. Once you destroy it Navi will go green in the center of the room.
This one requires two bombs to destroy instead of one. Go through it and down the passage, where you'll reach a Big Beamos. Put on the Hover Boots and run straight as far as the boots will take you to get to the doorway. When you've pointed the statue at the right skull, they will all light up, and the door at the end of the chasm will open.
