Every once in a while, though, I got a brief glimpse behind this idyllic curtain. As I walked up near the Seine, I passed an old brick high school, glanced down the road to my left and stopped in my tracks. There, hidden until now at the end of the street, was a modernist skyscraper, the Tour Evasion 2000, rising awfully, dejectedly, above its surroundings. And yet it charmed me - so rundown, so out of place in what we think of as a grand, pristine belle époque city. Beyond the tower, stuck between a busy road and the quais of the Seine, was a narrow strip of parkland, a group of homeless immigrants encamped at one end, a nearly naked woman sunbathing at the other.

From there I turned back east, where suddenly the landscape became oddly familiar. Right! Here, still in the 15th, was 47, rue Fondary, where 13 years ago my then-girlfriend, now-wife, Jean, had lived as a student, and down the street the H?tel Fondary, where we'd spent a night after locking ourselves out of her apartment. That was the first in what would be a long series of travel-related near-disasters - our calamitous Mexican road trip, our jet-lagged toddler's miserable Taiwan visit - and while I remembered it now fondly, I also felt strange. I'd been whipsawed back and forth between the new and the nostalgic - and I kind of liked it.

This disconcerting though pleasurable phenomenon - the past inserting itself into the present - happened again and again. Another day, back on the Right Bank, in a part of the 12th Arrondissement I would've sworn I'd never visited, I stopped for lunch at a cafe, Au Va et Vient, and at one of the outdoor tables enjoyed a hearty bowl of duck confit with sweet carrots while the man next to me distractedly tried to read a Paul Theroux book. Nothing I could see on the broad boulevard - trees, fountains, people strutting purposefully into the Métro - gelled into memory. But afterward, I walked a half-block and found myself at Raimo, an ice cream shop founded in 1947 that also sells sacks of toasted almonds, a lesser-known delicacy that a friend turned me on to in 2009.

Then, just around the corner, I found a mysterious parklike path that led who knows where. Actually, I realized after a few minutes of following it, I knew exactly where. This was the Chemin Vert, the green highway that wends surreptitiously across the 12th, sometimes below street level, sometimes over an old viaduct and occasionally cutting right through buildings. And I'd certainly walked it before. In fact, Jean and I had dined beneath it, at Le Viaduc Café, a trendy spot (or so we thought) back in 1998. And I'd probably ordered duck confit then, too.

Before I had a chance to process this stumbled-upon memory, however, it began to rain. I opened my expensive umbrella and kept on walking.

Almost everywhere I looked in Paris I found this tug between the past and present engulfing me. The novel I'd picked up in a Marais bookstore - Haruki Murakami's "1Q84" - turned out to be a story of the past creepily inserting itself into the present. Of course. And Lars von Trier's provocative "Melancholia," which I caught in Montmartre, was about a dysfunctional family facing the ultimate eradication of their past (and present and future). It was as if Paris itself knew why I had come. Or maybe I was finally seeing Paris for what it really was: a marvelous open-air cinema where the filmstrips of our memories flicker ceaselessly, even as we shoot new scenes.

Any angst I had about the success or failure of my mission was fast evaporating as I was enjoying myself too much to care, and coming to realize that whatever I was doing, I was still participating in distinctly Parisian endeavors. Reminiscing at meaningful corners, indulging in highbrow culture available nowhere else, eating more duck than one should eat - this is why we come to Paris in the first place. This is why I'd come to Paris, and why I'd kept coming back.

That said, one day's excursion, to the busy but overlooked 13th Arrondissement, got me more excited than every other, because it was entirely new. Following a vague tip from a Drew Barrymore look-alike I met in a bar, I took the Métro to the Bibliothèque Nationale Fran?aise and hunted for Les Frigos, an artists' collective. Frankly, it wasn't a hunt. Les Frigos, housed in a craggy, turreted cold-storage warehouse built in 1921, instantly stood out in this new neighborhood of glass and steel. Inside, the walls had been decorated floor to ceiling by the generations of sculptors, painters and photographers who've worked here since the mid-'80s. Nothing was going on that day, but I didn't care. The building itself was worth witnessing, particularly because I'd never heard of it before.

To the west, the neighborhood was older, full of businesses like Le Cristal, a grotty, busy brasserie where a creaky-voiced waitress served me roast lamb in a flood of flageolets. But it also included a whole Little Saigon that I hadn't known about - street after street of Vietnamese noodle shops and vendors of cheap souvenirs. There was even some quirky history, like the Square Henri-Rousselle, where the first hot-air-balloon flight landed in 1783.

And right nearby, La Butte aux Cailles. How had I missed this neighborhood all these years? With its narrow lanes, clever street art and relaxed cafe-bars, it felt like a village in the middle of Paris - like the Marais minus the boutiques or Montmartre pre-"Amélie." I walked up and down the streets, then into the offices of Les Amis de la Commune de Paris, a group dedicated to preserving the memory of the few months in 1871 when a workers' movement took control of the capital.

"It's not taught in schools," lamented Fran?oise Bazire, Les Amis' secretary general. That bit of the past was fading.