To unlock the original Prince of Persia game, you'll need to start from the Above the Baths save (once you have your new sword). Go down the stairwell that leads to a large cavernous area. After you make it through this area, you'll end up in a small room with Farah. There are a lever and a gear in the center of the room. Turn it clockwise until it clicks twice. Both doors in the room are now closed, but you'll also open a secret door that you cannot see. Go to the wall directly opposite the entrance. Swing until you find a spot on the wall where your sword doesn't spark. Strike this area a few times to reveal a hidden room. Enter to unlock the game, which is now available on the main menu.