Pls help me get past Level 28

I have activated 3 of the 4 pillars but, when I get to the 4th, it looks like ice covering a bldg, I see a symbol that looks like a water droplet. When I try to click on it, nothing happens. Also, it's not on the same bldg or same location each time I try. I viewed a walk-through, too. It doesn't look much like the game I'm playing.