BRAZIL IS THAT MOST WILD of contradictions: City of God goes to the beach. And in Brazil the beach is everything—two-thirds of the country's 186 million people live along the shore. Once, on the Costa Verde, east of São Paulo, my Brazilian wife and I were lounging on a short shock of white sand, hungry for brunch. Along came a man in a waiter's coat, who took our order for lobster. I watched as he slipped off his sandals, walked into the water, and grabbed a couple of bugs so fresh they pinched your tongue.

Two nights before, we had been club-hopping in Rio de Janeiro. Written on the famously sweaty wall of a dance palace called Estudantina was the slogan WHERE THERE IS DANCING THERE IS HOPE. In Brazil, no matter what else happens, there is always dancing.

The private house where we'd been staying near the city of Ubatuba was more of an estate, with counters of blue granite, floors of ocher travertine, and recycled hardwood beams. Everyone walked around barefoot with caipirinha cocktails made of good cachaça, a sugarcane spirit, and wandered off into the forest under the fat moon. But come Sunday night, all the guests left in fast cars for the city. Our host's caretaker came to see us. We were the only ones left in the joint, and the caretaker's house was at the other end of the property. "Nothing to worry about," said the man, and he handed me a loaded pistol. The pistol was more for the occasional wandering criminal than the hungry jaguar, I guessed.

Some say Brazil is not for beginners, a quote attributed to Tom Jobim, the famous musician who co-wrote "The Girl from Ipanema," a classic song from 1962 that has present-day meaning for me. It was 1984 at a Rio club called Jazzmania that I met a woman with bossa nova legs—my future wife, Inés Salgado. She'd grown up three blocks from the Ipanema bar where the song was inspired. The rest is—has become—three children and a good dozen wild rambles through the rainforests and down the rivers of a country that could swallow the continental United States and almost half of Alaska. Brazil stretches 4,000 miles from the humid Amazon, over the coolish Planalto Central, across seas of waving soybeans in the midsection, to a well-drained swamp called the Pantanal, one of the planet's largest bird sanctuaries, a swatch bigger than Florida, and past iconic yet sketchy Rio to São Paulo, a metro sprawl of 18 million and growing fast, before leaping out of the industrial suburbs to the spectacular Costa Verde, which is like Big Sur with string bikinis, and on down to straitlaced old Argentina, which is always trying to out-European the Europeans. Brazil, on the other hand, is confident in itself as a repository of sensual living and tapirs. Why else would the Europeans (and, increasingly, the Americans) keep coming?

Brazil's natural treasures are endlessly complex: Chapada Diamantina, Fernando de Noronha, Serra da Bocaina—whole areas as beautiful as the Grand Canyon, parts of the Hawaiian Islands, or the Great Smoky Mountains—not to mention Iguaçu Falls, which has more falling water than Niagara: All have been set aside as national parks, and yet few Brazilians use them.

In my experience, Brazilians don't like to camp. They're all at the beach, which runs, pretty much uninterrupted, for almost 5,000 miles. Brazil's many beaches vary from tranquil Trancoso, in the north, where you may ride horses on the deserted sand, to the array of thousands of fashionable Cariocas (slang for anyone who lives in Rio) on a cloudless Sunday in February on Ipanema Beach. Farther south, there's the Carnival parade at Florianópolis's alabaster-sand tourist paradise. For Americans, therefore, a hiking-kayaking-climbing tour of interior Brazil can be an uncrowded ramble in paradise, punctuated by the occasional European in lederhosen and little else, perhaps.

I've hang-glided São Conrado over the tops of the skyscrapers at the southern end of Rio, surfed Ubatuba, and scuba-dived off the coast of Arraial do Cabo, on Cabo Frio, in search of black sea horses. I've also baited wire-shanked hooks for tasty piranha while cruising down the Rio Cuiabá in a small riverboat as black howler monkeys called from the Pantanal's flowering trees, bony-nosed gators (jacarés) thrashed about in the wake, and those giant rodents called capybaras periodically jumped up to watch us paddle by.

Wild animals, cactuses, pineapples, rich people, poor people, soccer, and the world's tenth-largest economy—that's Brazil. The country is also a leader in the export of high-tech jets, steel, and architectural design. And it's full of smart, computer-savvy people. The gulf between rich and poor is even wider than in the United States, but the socialist regime of President Luiz Inácio Lula Da Silva (affectionately known as Lula, a family name that also means "Squid") is trying to make things better for the most disenfranchised.

Environmentally, Brazil really is changing. Not so long ago, the Amazon was often considered by those urban coastal dwellers a Green Hell, to be chopped, pulped, trampled by zebu cows, and fought against with every herbicide known to Dow. Much has changed since Chico Mendes was gunned down. Brazil has pretty much outlawed cattle grazing in the rainforests, tried to rein in destructive cyanide-leach gold mining, and started protecting those few indigenous peoples the Portuguese didn't massacre 300 years ago. Now the country gets deservedly high marks as an eco-experimenter, a leader in innovative mass transit, refuse recycling, sustainable agriculture, and other pastimes, the most fascinating (and contradictory) being biofuels. Brazil no longer needs to import any oil, since 90 percent of all new vehicles run on sugarcane ethanol mixed with Brazil's own major deposits of offshore crude tapped by high-tech drilling. Ironically, the greatest new threat to the Amazon is soy—which is increasingly being converted to biofuel. The current price of oil has made it hugely profitable to mow down the Amazon once again, this time to plant soybeans to run cars.

Some come to Brazil to research biofuels, and many hope to see a capybara, sure, but what most recently upped the temperature of the country's already quente zeitgeist was the arrival of the Brazilian model. Brazil exports healthy six-footers (men and women) the way China exports Christmas-tree ornaments. It didn't hurt that Gisele Bündchen (Leonardo DiCaprio's ex) was declared the most beautiful girl in the world by Rolling Stone in 2000, or that Daniela Cicarelli (ex of Ronaldo—did I mention the country's pretty good at soccer, too?) did a languid stand-up "samba" in the surf with her banker boyfriend that was rumored to have nearly crashed the Internet in Brazil, so popular was the pirated paparazzi tape. But what's truly Brazilian about this whole thing is that Cicarelli is a triathlete, not some London cocaine waif, just as Bündchen dreamed of a professional volleyball career before the runway beckoned. In Brazil, spiking is as important as strutting.