Mace Weapon
After reaching the top of the waterfall area, to the left of the switch you pulled is a tall tree. Swipe at it with your sword until you make contact. A ball will fall from its branches. Take the ball up the stairs, into the opened room, and drop it. You will notice tree arches between the two stairs going to the upper level of the room. Go to the middle arch and push on one side of it to make it revolve and reveal a secret room. Go back and take the ball (and Yorda) and enter the secret room . Hop into the idol pedestal with Yorda and a basket will appear. Take the ball and shoot it into the basket. A mace will fly through the window. It is more powerful then the sword and the 2x4. You can take out a standard Ghout in three swings.

Beating the Final Boss
When fighting the queen, the energy sword is paramount. Whenever you are holding it, her shadow attacks cannot touch you. If you take a hit without it, however, you will turn to ash. The way to beat the queen is to hack at her shield with the sword. Once you hit it, the sword will fly from your hand and you'll have to retrieve it. Immediately after hitting the shield, run behind one of two statues at the center of the room. The shadow attack will pass you by. From this position of safety, scan the room for your discarded sword. The first time it is rejected, it will end up in the right side of the room. The next three times, you will find it on the left side of the room. After four hits, the queen's shield will drop. This time, your sword ends up well behind the statue. Hide behind the right statue. As the shadow passes, you will notice a safe zone on the ground -- a kind of oval. Get as far back in the safe zone as possible. As soon as the shadow wave passes, head straight back from the statue and run to the sword. You'll grab it just as her next wave reaches you. With the sword in hand, stride to the front of the room and strike the final blow.

Second Ending
After you beat the queen, wait until after the credits roll. Another cut scene will play, then you will take control of Ico on the beach. Move far down the coast to the left and you will find a surprise.

Turning wheels
When turning big wheels, as when shutting off the water, turn from the farthest point to go faster.

Avoid losing Yorda
To avoid losing Yorda, as soon as you set her free press R1 and hold her hand, then run to the door . You should also pick up the stick that falls so you can defeat the Shadow Creatures easily.

Finding Yorda
When in the last level with Ico's horns cut off on the beach, go towards the left following the shore of the beach to find Yorda.

Destroying the Smoke Creatures easily
If you enter a room, and it is a clear run to the portal on the other side, take Yorda by the hand and run her to the portal with the black Smoke Creatures chasing you. As you approach the portal, Yorda's activation of the portal will create lightning which will destroy the creatures anywhere near you.