Porteños love to brag that Buenos Aires has the world's widest avenue (Avenida 9 de Julio), its best steak, and its most beautiful women. The place to decide whether they're right is the city's heart, known simply as "Centro" or "El Centro," where many things merit superlatives.

For a start, this is one of the city's oldest areas. Plaza de Mayo is the original main square, and civic buildings both past and present are clustered between it and Plaza Congreso. Though you probably know Plaza de Mayo best from the balcony scene in the 1996 film Evita, many of Argentina's most historic events—including revolutions, demonstrations, and terrorist attacks—took place around its axes. Bullet-marked facades, sidewalks embedded with plaques, and memorials where buildings once stood are reminders of all this history, and the protesters who fill the streets regularly are history in the making.

More upbeat gatherings—open-air concerts, soccer victory celebrations, post-election reveling—take place around the Obelisco, a scaled-down Washington Monument look-alike that honors the founding of Buenos Aires. Inescapably phallic, it's the butt of local jokes about male insecurity in this oh-so-macho city. It's even dressed in a giant red condom each year on AIDS Awareness Day.

The town's most highbrow cultural events are hosted a few blocks away in the spectacular Teatro Colón, and the highest-grossing theatrical productions line Avenida Corrientes, whose sidewalks overflow on weekends with dolled-up locals. The center of Argentina's biggest scandals, the judicial district, is Tribunales, the area around Plaza Lavalle.

Building buffs get their biggest kicks in this part of town, too. Architectural wonders of yesteryear—French-inspired domes and towers with Iberian accents—line grand avenues. Dreamy art deco theaters and severe, monumental Peronist constructions mark the 20th century.

Contemporary masterpieces by such world-renowned architects as Sir Norman Foster and local boy César Pelli are filling adjacent Puerto Madero, a onetime port area that's now the city's swankiest district, with chichi hotels, restaurants, and shops. A promenade along the old docks affords great views of developments across the water in Puerto Madero Este; go across via Santiago Calatrava's Puente de la Mujer, a bridge whose sleek white curves were inspired by tango dancers.

Office workers, shoppers, and sightseers fill Centro's streets each day. Traffic noise and driving tactics also reach superlative levels. Locals profess to hate the chaos; unrushed visitors get a buzz out of the bustle. Either way, Centro provokes extreme reactions.