Any idea how to do this??

So, I've been building Gaudí's buildings, and I've found myself stuck on these two Casa Milá features. First of all, I'm only doing the shown corner on the floor plan image. so from the front we will see the corner, and from the back we will see the famous skylight with the fading color wall. Now here are my problems First of all, in the facade image we see the windows but I'm having a lot of trouble creating a frame for them because I've already figured out how to do the flowy wall thingy,...