If the only thing you leave here is your heart, you didn’t stay long enough.

My soul and the City of San Francisco are in a relationship. It’s complicated.

If you closely observe urban life for a living, you couldn’t imagine a better working town. The music, the art, the food, all of it from every culture and nationality. Crazy politics and crazier politicians. One part bazaar, other parts bizarre, all placed in a jeweled setting of hills, architecture, sea and bay.

Perhaps the most beautiful of American cities. If you’re a photographer, almost every shot you take here is a potential postcard. Few skylines anywhere burn their way more deeply into your memory than that of San Francisco from across Treasure Island on a fog-free night.

Apart from that, San Francisco just has the kind of urban sense of presence to which Los Angeles and Phoenix and Dallas can only aspire, in vain.

When my professional life as a writer and journalist began in San Francisco 40 years ago, I figured I’d spend my whole career here. It didn’t work out that way. But every so often, I have to renew my acquaintance with The City for a few hours.

First stop, the crookedest street in the world. No, NOT Lombard Street. It’s actually Vermont Street, in the working-class neighborhood of Potrero Hill, where O.J. Simpson grew up, not far from the Mission District.

It starts at the little McKinley Square park at 20th Street and winds down seven serious hairpin turns to 22nd. Misjudge any one of those seven turns and you’ll find yourself in someone’s driveway — or their living room.

You know that Kia automobile commercial, the one in which a friendly motorist offers a stranded cabbie a lift, then takes him on a wild ride down the tightest set of switchbacks you’ve ever seen in a city?

That’s Vermont Street.

Lombard has more turns and more hype. Vermont is steeper. The geeks will tell you that Vermont has greater “sinuosity.” Having driven both, I can tell you I wouldn’t take a skateboard down either one.

Today, it was just Vermont. Right-left-right-left-right-left-right. By the time I hit the bottom, I was grinning from ear to ear.

All those curves spun me toward downtown, Market Street, still the commercial heart of the city. I didn’t have a car when I started out here back in the day, but you could get around San Francisco surprisingly well on streetcars.

Apparently, you still can.

Nowadays, though, the streetcars can transport you in more ways than one. The city runs historic 1930s vintage PCC streetcars and antique trolleys from 14 American cities and countries as far away as Italy, Germany, Russia and Japan, each in their original colors.

For train nuts like me, seeing all these different rolleys on the streets in The City — not only from different cities, but different countries — is just entirely too cool.

Especially when you realize just how much history each of those streetcars represents.

DID YOU KNOW?
I didn’t when I took that shot from my car, but that Philadelphia streetcar represents a milestone in black Civil Rights history.

It was the summer of 1994, at the height of World War 2. Because of manpower shortages, the Philadelphia Transportation Co. was under pressure to let black employees run the streetcars.

The white PTC employees weren’t having it. When eight black streetcar “motormen” were preparing to make their first trial run on Aug. 1, they staged a “sickout” that paralyzed Philadelphia for a week. In a city full of war factories and shipyards, thousands of people couldn’t get to work.

The Army moved in and ran the streetcars, but the strike didn’t end until Washington threatened to revoke the strikers’ draft deferments. Throughout, the new black motormen stayed on the job, to be joined within a year by hundreds of others.

Had I known all that, I might have sat up just a little straighter as that Philadelphia streetcar — and its black motorman — rumbled by.

After that, it was off to the Presidio for a little game of historical “what-if?”

Back when the Presidio was a U.S. Army base, you only got the most fleeting glimpse of a few strange concrete structures amid the trees as you drove toward the Golden Gate Bridge.

The Presidio is now part of the Golden Gate National Recreational Area, open to all, and you can see for yourself what all those wind-shaped trees were hiding all those decades.

A modern-day fortress.

Those bizarre structures were meant to hide coastal artillery, 35 gun batteries on both sides of the Golden Gate to defend San Francisco Bay from invasion, a very real fear after Pearl Harbor. Some of those guns were the size of a house, able to throw a half-ton shell nearly 20 miles.

Could these batteries have stopped a fleet of Japanese battle fleet, or would they have been shattered and their exposed gun crews slaughtered? The guns themselves are long gone, but the batteries remain, a curiosity for tourists, a magnet for taggers, a burning memory for the aging veterans who stood guard here against an invasion that, thankfully, never came.

There is one invasion that swept over San Francisco decades ago and never left — a horde of great places to eat. This is a foodies’ paradise. Whole streets and boulevards are devoted to restaurants of every style and ethnicity.

On one of them, Geary Street, you can practically eat your way from downtown to the ocean, and navigate a world of tastes as you do. Italian and Vietnamese stand next-door to Chinese and French, across the street from Russian and Thai and around the corner from Ethiopian and Korean, with a few steakhouses, produce markets and cigar bars thrown in here and there as points of reference.

All of them are local joints, not a chain resto in sight.

Whatever your taste in food and drink, if you can’t find it here, you might as well stop looking.

Not sure what to have, what you want? Just drive around with your window rolled down and follow the aromas. Ginger, garlic and sesame oil. Maybe it will be cardamom, chili oil, wood charcoal and lemongrass.

It was just a quick three hours or so, just long enough for a partial reminder of why I left my heart, soul and God-knows-what-else here. It’s a relationship I barely understand, and definitely can’t explain. To paraphrase a U.S. Supreme Court justice, I can’t tell you what it is, but I know it when I feel it — and I feel it whenever I’m here.

Some folks don’t understand why Tony Bennett is still performing his iconicsong, “I Left My Heart in San Francidco” at the age of 84. I do, and if you ever visit here, odds are you will, too.

Sing it, Tony. Sing it…