Going Down
Okay, technically you guys are already in the Solarium, i.e., the Solar Observatory, i.e., the 10th floor. I think you're talking about the Botanical Gardens. So down you go to the 4th level.
There's the fountain and main stairs that Otto warned you about, and the greenhouse... both remain unexplored. You head on over to the fountain to see what Otto was all worked up about.
The fountain is rather nasty... the marble is cracked and dirty, and rather than nice, clean flowing water... it's full of a viscuous broth, mostly clear but with odd chunks of things.
As you approach to get a better look, the broth itself rises out of the fountain like a giant blob. You look at each other for a split second, and then it divides itself into different, vaguely PC-shaped sub-blobs, one for each of you. One blob advances on each of you. You guys have init.