This is what I'm trying to model:
I'm stuck here. I don't know how to go about creating the door of the castle. I've tried adding the cavity with a boolean modifier and solidifying the edges around, but the result is far from acceptable.
What is the smartest way to go around this? Subdivide->Knife?
PD: I added the .blend file just in case you want to give it a try. I'm interested in learning the process, not in having the result finished. I'm here to learn.