When you make it into the City Gardens and have deactivated the Sand Gate, you will encounter a large round sunken arena which is patrolled by four Sand Guards. Speed killed them both with "double kills" then drop down into the arena. You will be confronted by the Stone Guardian, which is really just a different looking Thrall from Prince Of Persia: Warrior Within, which means you will initially deal with him in the same way. When you are in front of him, roll between his legs then attack the back of his ankles. After a only a little of this he will drop to one knee, just like the Thrall. Climb up on his back, just like the Thrall, but this is where the similarities stop. After you have climbed up on his head you will stab your dagger into the back of his neck, which will enable you to steer him like the chariot. As soon as you gain control of him, lead him through the large, closed, wooden door in the arena then through another door in the adjoining room. As he is running, the giant speeds up and this makes it much more difficult to control him. However, if you brush him up against the walls, he slows down to a manageable speed. However, make sure you only brush the walls or he will crash and land on top of you.