[Davros]

It's a bit hard to describe when I don't know exactly where you have been. After you use the catapult, you can walk down from the battlements into the gardens. From there you can walk about till you get to what I think of as the main street (ie the trap with dummy on the right, and the entryway to the idol room on the left. From there you can go back up the stairs to the other set of battlements.