This is not as fancy as the ones I see in this discussion, but I was trying to do what was asked of me. I could have used transforms and modifiers. I did not because I feel that the best way to experience Blender 2.8 is to explore each option shown thoroughly before jumping into too many variables. 2.8 looks so different that I want to make sure I understand each element thoroughly before jumping in with both feet (or hands).
So, here is my observatory with only a box as an added entrance door. Maybe not brilliant to look at but I used the add menu that pops up when you add an object to a scene.
