On Literary Hub, a second excerpt from Meet Me by the Fountain focused on this totally important question.
A stepped, centralized seating area appears, in one form or another, in most malls built in the 1980s. Sometimes there’s a fountain. Sometimes there are plants. Sometimes there is a sculpture. If the mall is multilevel, skylights illuminate the space from above. Escalators traveling between floors make for easy, surreptitious people-watching. Is my friend hanging out at the mall? Is my crush? This is the atrium, the most important interior space of the mall for the adolescent both architecturally and psychologically.
The earliest indoor shopping malls, with their I-shaped, bowling-alley forms, had no centralized place where groups could gather, nor much need for one. But by the early 1970s, and the advent of more complexly laid-out malls in T-, X-, or O-shapes, patrons might wander forever, missing each other in the long, low-ceilinged identical halls. Hence the atrium, which has its own storied architectural history: Ancient Roman houses were centered on open-air or skylit spaces, which provided daylight and breezes to the rooms surrounding them.
These courts often had an impluvium, or fountain, to catch rainwater from the roof, as well as furnishings for outdoor entertaining. In the shopping mall, the atrium serves a similar function, opening up the middle of a building lined with windowless shops; letting in light, water, and plants; and furnished like a living room. The atrium was the center of the social life of the Roman domus and so, too, has it been the center of mall sociability.
Gruen envisioned Southdale as an ersatz town green and, indeed, some of that civic sensibility remains in the symmetry and greenery of mall atriums. But the theatrical aspect of circumnavigating, posing, or performing in that centralized space makes this green seem more like the gossipy New England of Peyton Place than the buttoned-up town squares of earlier American depictions.