Here I’ve studied Bryce 4’s boolean modeling capabilities when I was designing that building for this scene. That antenna on top of the building was done with Realsoft’s Real 3D though. At first I tried to use only cloud spheres with this scene but I soon noticed that it didn’t work at all because the sunlight comes from wrong direction. So I dumped the spheres and used cloud layers instead. When overall look of the sky was okay I created a few cloud spheres to get some detail where I wanted to.