OK, go back into the next room, up the ladder, up the chain. Go out the door and then head right, and go back into the room on another ledge. Go up the long ladder on the left - ignore the short one. Jump to that central chain, and it'll pull down, raising the floor with it. Of course Yorda, who I normally leave right in front of the icon doors, has stepped away! Ah well.

Press and hold O and then use your stick to get the chain swinging. Swing up to the upper level. Monsters will of course attack, so jump down to kill them. Then swing back up onto the upper level. Go to the edge and call to Yorda. She'll jump up to be with you. Go through the icon door.

The Ico Walkthrough

Please swing by my Forum to ask me how to get through if you're stuck somewhere I haven't put up yet. I'll get back to you quickly.