I was listening to Porcupine Tree's Fear of A Blank Planet the other day and was absolutely mesmerized by the soundscapes in certain songs. Which has lead me on a search for bands that just purely soundscape. Does anyone know any?

That's pretty vague. There are several huge genres focused on soundscapes. I guess you ought to make your way to The Ambient/Drone/Modern Classical topic so we can get some life there. If you're not actually looking for ambient, what moments of what songs do you actually mean?