The Forgotten City

This is obtained in the Undercity after collecting the Egyptian and "Mystery" plaques. After picking up the mystery plaque you'll follow a linear path to reach the surface. Along the way you see 3 large circular pressure plates on the floor. Simply step on each one to release a boulder which can be easily "dodged" by stepping to the side. Final plate is where you confront Khabash at the stairs before exiting.