broad, as there is a wide range of things to explore in the subject, so it is a large/ broad subject. Science for example has biology, chemistry, and physics under it, and many things under each of these subtopics, which is why, science is a broad topic/subject, whereas if you were to narrow it down to the atoms (Chemistry) it would be less broad. and more limited, any subject can be impressive, no matter how limited nor broad it is.