When you reach the pool, you'll have to fight all of the Harpies and the Medusa in the area for the path to open up. You'll then see a cutscene featuring an old man digging. Then, go up the staircase and to the left of the Temple you should see a chest. Open it for a Phoenix Feather. To the right is another chest containing a Gorgon Eye. Now go up the staircase inside the Temple.
In the Temple
After a while of walking up stairs, you'll reach a room where a cutscene will show you Harpies coming out of gaps in the walls. Don't bother fighting them, as they'll only keep coming. What you have to do is go to the front of the room where you'll see two statues. Pull the left one down to cover the first gap, pull the right one down to cover the right gap. The Harpies will stop coming and then you'll be able to kill the remaining ones. Go to the gate by the entrance of the room and lift the gate with . Go up the next staircase and then balance on the beams to get across to the other side of the room. You'll know when the beam is about to fall when you walk near it, so make sure you don't step on any weak ones or else you'll have to start over. Afterward, just follow the path (killing the enemies along the way) until the cutscene.
Rescue the Oracle
After the cutscene, go for the statue by the entrance and push it off the ledge. Then take the other statue and push it on top of that one. When that's done, one statue should be on top of the other. Drop down and push the statues until you reach an area with a ledge and a platform supported by columns. Push the statues between those, then jump on top of the platform supported by columns by jumping onto the ledge with the red chest. Then jump onto the statues you placed to reach the ledge. You'll then see a cutscene and a timer will start. Jump onto the vines and climb to the left toward the gears. Jump when the gears stop turning, then keep climbing the vines until you reach a rope. Swing onto the ledge, balance through the next platforms, jump onto the rope, and swing onto the dish of water held by the statue. A cutscene shows Kratos saving the Oracle, and then a flashback from Kratos' past. Then go through the door the Oracle just opened and climb all the way up the stairs through the mountain for a Phoenix Feather. Go back down, then go forward into the large statue and down the spiraling staircase. Open the chest by the stairs for another Phoenix Feather, then jump into the gap and enter the Sewers of Athens.