I am in the elvan city and have killed everything and opened the palace gates. I recovered the harp, the pipe thingy and both types of nutz..Now what there is nothing in side the palace except the tree room and the water fall room.... What do i do?

SPOILER
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Go into the waterfall room, and look about, examine the waterfall, the pool, and the other items in the room. You should be able to figure out what to do next.