Re: best phrasing
I applaud your efforts to use more creative vocabulary, but "perched" makes it sound like they are (maybe) not very stable, and "rising higher and higher" could make someone think that the buildings got taller (each building taller than the next, instead of starting at a different height).
Are you allowed to be creative? Can you say "Houses make their way up the (steep sides?) of the hill until the nestle in the shadow of the cathedral, magnificent at the summit" or something like that?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.