So, how does exactly works a minor-major system, and what someone wishing to have an Architecture graduation would have for undergraduation?
A major is a subject that you choose to specialize in when you recieve your bachelor's degree. Different professions require different majors (to be a teacher you would major in education, for instance). There are a certain number of classes dealing with the subject that you are required to take and then when you graduate your diploma says you majored in the subject.
Minors are similar to majors in that they have a certain number of required classes that you have to take and your diploma will say you minored in a subject, but the number of classes required is less than required for a major and most professions don't require you to minor in something.
Sometimes colleges will limit the number of majors and minors you can have, sometimes they won't. A lot of people don't minor in anything, and a lot of people with have two or three majors with a minor (or two) in there as well. Everyone has to have a major, but no one has to have a minor.
To answer your specific question, I'd assume you'd major in architecture (probably minor in either interior design or civil engineering or some such thing).