Go right when you reach the door with Medusa carving on it. You'll see a save point and a green orb chest. Go further right and watch a short scene. You'll find a key by the dead soldier's body. A few enemies will appear. Defeat them and go back near the temple. This time go to the left of the main gates. There are a few undead skeletons here - you can perform a cool fatality on them once they're weakened.
You'll reach a door that can be opened using the key you found. A little bit to the right of the door you can find a red orb chest (it's hidden behind a dark pillar). A few steps ahead there's another chest - this one contains a Gorgon Eye.