Gran Buenos Aires (Greater Buenos Aires) is a sprawling metropolitan area that takes in large parts of surrounding Buenos Aires Province. The Ciudad Autónoma de Buenos Aires (Autonomous City of Buenos Aires, also known as the Capital Federal) lies within the boundaries formed by the Río de la Plata, its Riachuelo tributary, and the Avenida General Paz and Avenida 27 de Febrero ring roads.
Buenos Aires ’s barrios give the megalopolis its neighborhood ambience. Its historic center is Monserrat  (also known as Catedral al Sur, “South of the Cathedral”), whose Plaza de Mayo  is ground zero in Argentine public life. Immediately north, part of the barrio of San Nicolás, the Microcentro  (also known as Catedral al Norte, “North of the Cathedral”) is the commercial and financial hub. To the east, stretching north–south along the river, redeveloped Puerto Madero  is the newest barrio.
South of Monserrat, tourist-friendly San Telmo  is a Bohemian blend of the colonial barrio, peopled with artists and musicians, plus a scattering of old-money families and even more conventillos (tenements) abandoned by old money. To the southeast, La Boca  has never been prosperous, but it has a colorful working-class history, a palpable sense of community, and extravagant vernacular architecture.
West of Monserrat and San Nicolás, Balvanera  subdivides into several smaller neighborhoods, including Congreso (home to the national legislature), Once (the Jewish garment district), and the Abasto (which gave the city tango legend Carlos Gardel).
Across Avenida Córdoba, Retiro  marks a transition to the upper-middle-class residential barrios to the north and northwest. Immediately northwest, elegant Recoleta  is famous for its even more elegant necropolis, the Cementerio de la Recoleta . Overlapping Retiro and Recoleta, Barrio Norte  is an opportunistic real estate fiction rather than a barrio per se.
Beyond Recoleta, several avenues lead to the open spaces of Palermo . One of the city’s most rapidly changing areas, the city’s largest barrio subdivides into several smaller but distinct units: the embassy row of PalermoChico, between Avenida del Libertador and the river; the residential and nightlife zone of PalermoViejo, across Avenida Santa Fe, which further subdivides into “PalermoSoho” and “PalermoHollywood”; and Las Cañitas, on the Belgrano border. There is even a newly designated “PalermoQueens.”
Belgrano  prizes its residential identity, but its leafy streets also have several museums and other cultural resources. More outlying barrios have scattered points of tourist interest, including museums, parks, and ferias.