At my school (MIT) there is definitely a campus, but it's so integrated into Cambridge that it's hard to tell where campus leaves off and the city begins. No walls or wrought iron fences, etc.
Fraternity and sorority houses are fairly scattered around Boston and Cambridge (even a couple in Brookline). There are 2 or 3 concentrations of houses and a few more isolated ones, but no "Greek Row". And not all GLOs had houses (mine didn't).
It's a trade-off - we don't have all the wide open spaces that a more rural campus would have, but we have all the cultural activities, restaurants, museums, etc. of Boston. I liked it - guess I'm a city girl at heart
