On college visits, I've found that I really enjoy having an isolated, pretty campus next to a big city. That way, there is still a small community feel while great opportunities just outside. The colleges I saw that are like this are Georgetown U and Johns Hopkins.
What other schools (of that caliber) are like that? Does that description match Berkeley, Stanford, Penn, and USC (which I have not visited)? I haven't been to UC Berkeley so I can't say for sure but I am under the impression that it's more integrated with the city and spread out than you are looking for. Stanford is pretty and isolated, but it's only near Palo Alto, which doesn't qualify as a "big city" and is definitely not very college student-friendly. there are bigger cities but those are quite a bit further away. Other schools that are as highly selective as the ones on your list that have independent campuses in or very near big cities are Columbia (NYC), Harvard (Boston), and Brown (Providence). Also, the Claremont College Consortium is located on a single campus about 40 minutes from LA, which might be too far for you. They are also smaller than those other schools, but because they are in a Consortium it feels more like one big school. Look at Claremont McKenna and Pomona if those interest you at all. Also Tufts University is a very short train ride away from Boston.