IF YOU DECIDED TO BUILD a city for 16 million people, you probably wouldn’t put it on swampy land around a tropical coastal lagoon in West Africa. But Lagos (pronounced LAY-goss), Nigeria’s largest city, defied planners and politicians.

Despite concerted efforts to shift the center of gravity elsewhere (Abuja replaced Lagos as national capital in 1991), this lively, shambolic, infuriating, colorful metropolis continues to expand and thrive, establishing itself as the fourth-wealthiest city in Africa after Johannesburg, Cairo and Cape Town.

Wealth probably isn’t the thing you think of at first sight. Large sections of the city give over to smoke-shrouded shantytowns, home to two-thirds of the population. One such shanty, Makoko, spreads out into the lagoon as a vast, dense jumble of rickety wooden houses built on stilts.

By extreme contrast, a new Lagos extension is currently being built on reclaimed land adjacent to the affluent Victoria Island district. Eko Atlantic will initially be home to a quarter of a million residents, with a skyscraper skyline reminiscent of Dubai or Singapore. The new development is already creating waves in Lagos — literally. The reclaimed land altered the coastal currents and made other sections of the shoreline vulnerable to ocean surges.

Which district is representative of Lagos? Ramshackle Makoko or futuristic Eko Atlantic? For me, there’s no contest. Makoko remains the true embodiment of Lagos.

Yes, Lagos boasts an emergent middle class for whom Eko Atlantic proves the aspirational pinnacle. But the majority of the city’s inhabitants subsist from day to day in borderline poverty. Makoko, with its houses patched up with plastic sheeting and rusty corrugated iron, lapped by water swilling with pollution, seems at first sight a nightmare of destitution.

But look closer and you’ll find a thriving, dynamic community. Floating churches and schools help to provide social cohesion amid the chaotic sprawl. There are shops and basic services. Dugout canoes provide the main form of transport.

Nobody knows precisely how many people live here: perhaps as many as 300,000. With their extraordinary resilience, the inhabitants of Makoko embody the spirit of Lagos.