How many lives can one city have? Quite a few if the city is Berlin.

Royal capital, imperial seat, economic powerhouse, center of enlightenment ... before becoming a synonym for decadence in the 1920s and '30s, then a Nazi stronghold. Bombed, invaded, occupied in World War II. Suddenly divided in 1949, exuberantly reunited in 1989, and now again the capital of a unified Germany.

This year marks a quarter century since the fall of the Berlin Wall, and Berlin continues to boom amid the reminders of its extraordinary past-a complex, sometimes dark, history it is intent on neither forgetting nor denying.

I was a boy the first time I saw the Wall, a 96-mile barrier erected in the 1960s by the Communist German Democratic Republic (GDR) to isolate non-Communist West Berlin and keep GDR residents from defecting.

My family lived in Poland intermittently in the 1980s while my professor mother researched its political system. Periodically we'd make the long drive to West Berlin for provisions. Each time that the Wall, a ribbon of reinforced concrete topped with barbed wire, would come into view, my body would tense. We'd join the lines of waiting cars at closely guarded Checkpoint Charlie, the main crossing point for Americans. Stone-faced guards in grayish uniforms would peer into our car, study our faces. The tension was palpable.

When they waved us through, I'd watch in awe as the bright colors and lights on the Western side rushed toward us-neon signs on shop-lined Kurfürstendamm, supermarkets full of produce, streets filled with traffic-all a vivid contrast to the monotone, slow-moving cityscapes of Poland and East Germany. Those memories made West Berlin synonymous with sophistication, excitement, and abundance.

In 2005, I moved to the city, in part for the avant-garde art and music scene but also to live in a place where centuries of history were informing a new urban vision. I learned German, then met, and married, an American opera singer who'd been compelled by Germany's passion for classical music to move there.

Folks like us, flocking here from other parts of Germany and from around the world, have helped cement Berlin's reputation as a capital of creative ferment. We're even contributing to a new, multicultural German future. My wife and I had a baby Berliner in February-and were not surprised to find the hospital's maternity ward reflecting the city's diversity. We heard lots of German, but also English, Polish, French, Turkish.

I'm the first to admit there are parts of the city I don't know as well as I'd like. But this is not an easy city to fathom.

"Berlin has no real center, just neighborhoods," says Berliner Ulrike Poppe. "And each is very different."

So I headed out to four neighborhoods to find true locals who would show me my adopted city through their eyes, to deepen my understanding of how Berlin has changed in the 25 years since the Wall tumbled, to find vanishing vestiges of the Cold War-and to see what may be in store here in the future. ...