The geography of Cambridge is inexplicably organized into more than a dozen “squares,” which are actually anything but. The heart of them all is Harvard Square, a spider web of streets outside the walls of Harvard University that is crowded at all hours with students, parents, professors, and tourists.

Gone are the days when Harvard Square was a downbeat mecca of bars and used record stores; the chain stores have long since swallowed up all but a few struggling independents. Still, there’s something about strolling the brick sidewalks or people-watching from an outdoor table that is quintessential Cambridge.

When the weather turns balmy, street performers flood nooks and crannies, offering everything from folk music sets to magic acts, and turning the Harvard Square area into a spontaneous carnival. Equally satisfying is a stroll down Brattle Street, the heart of Cambridge literati, where John Kenneth Galbraith, Robert Reich, and other leading political lights inhabit miniature colonial mansions.