Not much of a secret as it is quite obvious. However, I kinda thought I should add it anyway. In the center of the room is a monument with four dolphins spreading bubbles. When you sing at it, it will spiral up and then release itself spreading the bubbles kinda everywhere. Well. Nothing spectecular, but at least some action!
Now this is actually a real secret in the gallery. There are two wheels in the room, one at the left side and one at the back. Sing at one of them and it will move. While it moves quickly sing at the other one. This will cause a mechnism that activates that large circular platform in the center of the room. It will lock down by circulating and then move up revealing a hole you can swim through. At the bottom are some light sticks and a tunnel. Swimming through it will get you to a new room which is just below the Domain of the Foe Image Gallery! You can look through the ceiling of this new room or rather the floor of the Image Gallery because it is made of semi transparent glass. But that's also about it already.
Another toy to play around with, just like in the first image gallery. At the top of this room is some organic... alien... something. Sing at it and it will release some green spots which fall the whole room to the bottom. Kinda nice and disturbing at the same time!
So, that's all that can be said about the gallery! Hope you liked it!