Take Yorda over to the elevator and get on it. Operate the switch to cause it to rise. They exit onto a mostly fenced in area with a switch set too high in the wall to reach. The fencing around this area is broken at one point and it looks like Ico can climb down there. Stand near the edge and have him climb down onto the ledge below, then the ledge below that. He then needs to climb up onto that ledge. Now head to the left, then jump up on the top ledge. Continue to the left and press the 'X' button to drop down to the ledge just below, then the one below that. Finally drop down to the wider ledge. Walk around the corner and straight ahead as far as possible, then climb up the next two short walls. Walk left a little ways, then jump up onto the ledge and move Ico left until he's got a straight shot up. Climb up onto the top ledge and move to the right to the opening. Climb up onto the wooden platform. Jump off and go over to the moveable block and push it down into the area where you left Yorda and drop down as it's obviously time for more spirit monsters to attack.

A black pool will appear just to the right of the box. Have Ico stand next to it and start flailing away as soon as they start coming out. There'll only be a few of them and they should be easily dispatched. If one of the flying ghouls does manage to take off with her, she'll be taken down to the black pool below, where the elevator came up from. In that case, high tail it over to the elevator and attempt to get back down and pull her out before it's game over. Once they're all dispatched, have them get back into the elevator and head back up.

Ico should next pull the block over beneath the switch on the wall. Have him climb onto the box and pull the switch, which'll cause a chain to be lowered, that he needs to get to next in the Stone Pillar area. Walk off of the box and pull the block back over to where it came from. Climb up onto the block and then up onto the area above. Turn and call Yorda and help her up. Go over to the stone couch and save.