Macabéa may live in a major city, but the actual physical spaces that she inhabits are quite limited. As the narrator puts it: "Acre Street for living, Lavradio Street for working, the docks for excursions on Sundays" (3.73).
But she didn't start off in the big city. Originally, she came from the backwoods of Alagoas, a poor, Northeastern coastal state. We don't learn much about this setting, except that it was brutal: her aunt beat and deprived her. Still, it's home, and it defines her so much that she feels an immediate kinship with other Northeasterners.
After her aunt dies, Macabéa ends up on Acre Street, in a slum in Rio de Janeiro's red-light district. Our narrator seems a little obsessed with Acre Street, and not in the good way. It's near the docks, where women try to pick up "seamen in the streets between the depots [warehouses] of charcoal and cement" (3.69). Sounds nice, right? Even the narrator stays away, actually "terrified of that dark hole and its depraved inhabitants" (3.70).
But Macabéa doesn't see it that way. On the contrary, "those polluted docks made the girl yearn for some future" (3.69). Except for right after she visits the fortuneteller, this is the only time we see Macabéa think about her future at all—so, something about this setting is working for her.
One thing to keep in mind is that Brazil is a big, not always happy, mix of ethnicities. The Portuguese colonized Brazil in the 16th century, Africans entered the country as slaves, and various other European, Middle Eastern, and Japanese immigrant groups came to Brazil starting in the mid-19th century.
But distinct social classes in Brazil originated in the early 1950's, when the country experienced economic prosperity that lasted until the late 1970's. These social classes depended a lot on geographic location, education, and occupation. On the one hand, we have the narrator who is clearly educated, urbane, and sophisticated.
On the other hand, we have people like Macabéa, Olímpico, and the Marias Macabéa lives with. They were born in rural areas, had little access to education, and seem culturally impoverished—so impoverished that they can't even define "culture." Macabéa doesn't even hear music until one of her roommates lends her a radio.
Macabéa's ignorant mind is more a mental setting than a physical setting, but it's just as important as the harsh realities of Acre Street. After all, it seems easier for Macabéa to move into the city than it does for her to move into a reality where she knows about things like "algebra" and "spaghetti."