There are people who are unafraid of Class V rapids, yet won't even consider a trip to India. The poverty and dirt – or at least the perception of these things – hold back otherwise hardy souls. But in actuality, Mumbai (formerly known as Bombay) is bursting with color, diversity, and adventure. Most surprising, though, is the thriving nightlife.

"Today, in your boring New York City it is illegal to even smoke, while Bombay is on fire – the best nightlife in Asia," an Indian gadabout who lives in the city explained. 

This seaside megalopolis is famous as the home of Bollywood, India's zany movie industry, which produces more films every year than Hollywood and sells more tickets. The same off-the-wall energy that fuels the films – there seems to be a mandate that chick flicks and shoot-'em-ups alike have at least three completely random song-and-dance numbers – is mirrored in the city's soul.

We started out at Masala Kraft, a funky nouvelle Indian restaurant at the Taj Mahal Hotel – the focus of the 2008 terror attacks – downtown. Afterward we walked several blocks to Indigo, a Thai restaurant and bar with a cliquey clientele who order expensive drinks as they gaze at the modern art on the walls. At 12:30 we caught an ancient Ambassador taxi – a relic from the colonial days – to the nightclub Athena, where we quickly got caught in a crush of bodies. House music bounced off the walls and strobe lights beamed onto exposed flesh.

According to movie producer Vikram Chopra, "Indian culture has loosened up. It's true that Bollywood's movies are sexy, with lots of skin and wet saris. But deep down the culture is still the same: We report to our parents. Even the biggest stars live at home if they're not married. You won't ever see people kissing in a club." Based on the scene that night, Chopra is right. The attitude on the dance floor was somewhere between ultrachaste and supersultry. Moves were suggestive, but bodies never intertwined.

The next morning, we caught a cab to the commercial area of town, called Crawford Market. Real life in Bombay is lived on the streets, and this is the best way to get out on them. There was movement everywhere. An ox cart piled high with rice nearly ran over a pedestrian while a belching Fiat taxi passed the other way, brushing aside laggards with a dented fender. An old man sat in the middle of the street for no apparent reason, a crash helmet on his head, while a group of women in splendid saris split around him like water around a rock. The variety of people is dazzling: Sikhs, Hindus, Muslims, Christians, and Jains, identifiable by the iconography around their necks, on their foreheads, or twined about their heads.

Late in the afternoon, we turned onto a side street, entering one of Bombay's many shantytowns. We passed through a curtain of flies and into a maze of dirt roads and eventually exited through a passageway that opened onto the Arabian Sea. There was a seawall 10 or so feet high, with children perched on its edge and jumping into the water. One boy turned his head and smiled, his back shining in the sun, before he propelled himself off. Moored in the bay, 40 feet away, were some small fishing boats, each flying a brightly colored flag blowing in the wind like a plume of rainbow smoke.

Not a quarter mile off, the Taj rose majestically into the Mumbai sky. Tonight the streets here would be crowded, industrious, frenetic, and spots like Athena would be equally packed with people writhing to booming music. These are the contrasting worlds that make up this crazed, amazing city, and you can't truthfully say you've been to Mumbai if you haven't seen both.

More information: The opulent Taj Mahal Hotel (from $295 per night) is centrally located for nightlife and sightseeing. The Gordon House Hotel (from $113) has bright, airy rooms. The Taj's Masala Kraft (dinner for two, $140) serves modern Indian food. The Taj's concierge can give you directions to Athena and Indigo.