Tower

Whale Room
The enterance to the whale room is located on the outer wall of the level, more or less below the exit to Snow, it can be easily located when the goo level is raised, the animation of the whale swimming out of it will give it away. You can easily get inside. The room itself is circular and has plenty of carpets hanging down on the walls. There is a hidden area behind the carpets that goes all around the room. If you go behind the carpet on the left from the enterance (from the "as you're entering" perspective), you can find a glowing symbol. Sometimes when the goo level is raised to the top, you can find a Flow Creature swimming around behind the carpets. Also there is a glyph/tapestry in the middle of the room. If the goo level isn't high enough and the whale didn't come out, you can find him at the top of the room.

Videos
No-commentary playthrough, including the Sting: https://www.youtube.com/watch?v=wiAF5bKYd-A&list=PLgc4x19qA79GkpkccBaXAtaUzDiz9lIsZ&index=6

Next Level
Snow