Townies is a series about life in New York, and occasionally other cities.

Townies takes a summer vacation from New York, with a month of essays from the cooler coast of San Francisco.

I got a bike — a fixed-gear with bright blue wheels, custom-made to my specifications. I am a San Francisco techno-hipster, so this selection was a bit of a self-caricature. But sometimes the predictable thing turns out to be the best thing, too, and you can’t let that stop you. When I went to receive my bike from its maker in a cramped workshop down on Cesar Chavez Street, I didn’t know what I know now: a single San Franciscan in possession of a good bike must be in want of a Wiggle.

I got the bike and I started to ride it. Gently at first. Tentatively. When you’ve biked only on quiet cul-de-sacs and college campuses, the idea of riding in the city, right up there alongside the cars, seems frankly pretty absurd. So in those early days, I picked my path carefully through quiet avenues. I pedaled exclusively on side streets with no stop lights.

But slowly I gathered my courage. It began with a Saturday foray down Market Street, San Francisco’s ugly, angry main artery. I didn’t get flattened or flung over the handlebars and I liked the look of the tall buildings blurring by on both sides. Next, I wanted to ride my bike to work — but I couldn’t quite figure out how.

San Francisco is spotted with steep hills, and in the middle they mass shoulder-to-shoulder like a defensive line, splitting the city in two. To the west, there’s Golden Gate Park and the long avenues of the Outerlands, the grid that stretches all the way to the Pacific; to the east, there’s the Mission and Market Street and the glistening bay. To the west, my apartment; to the east, my office. The train that takes you from one side to the other tunnels through the heart of a hill. If you drive it, your car labors up one side, teeters at the top, then pitches down the other.

Wendy MacNaughton

But there is no tunnel for bikers, and bikers can’t climb those streets. (Well, maybe some bikers can. This one couldn’t.) The shallow grade outside my door left me breathless, and the hills that separated me from downtown were much, much steeper. I cursed the blue-wheeled bike for its lack of mechanical advantage.

And then I heard about the Wiggle.

The Wiggle is not a secret, not exactly; there is a detailed Wikipedia entry. But you would never know to Google “the wiggle” unless someone told you about it, right? You would never know the Wiggle was even a thing unless one of your techno-hipster co-workers, also in possession of a fancy flat-colored fixed-gear, upon hearing of your plight, said: “Dude … you know about the Wiggle, right?”

It is the path between the hills, a very specific route defined by two very special geometric characteristics: (1) It zigzags crazily, block by block, and (2) It is relatively flat. Back when San Francisco was still called Yerba Buena, it was, in part, the path of the Sans Souci Creek. It was the path, legend has it, that Juan Bautista de Anza took south from his fort in the Presidio circa 1776, looking for a bit of greenery among the dunes. It was, and is, the path of least resistance.

The first time I set out along the Wiggle, I carried a wrinkled receipt with the street names scrawled in blue ink on the back: Fell, Scott, Haight, Pierce, Waller, Steiner, Duboce. Through the first few turns, I checked and rechecked my cheat-sheet, but by mid-Wiggle, I realized that no cheat-sheet was necessary. The flattest route was obvious — in fact, it was marked on the pavement with faded arrows — and more important, the flow of bikers was thickening.

This, even more than its flatness, is the power of the Wiggle. It’s a funnel. I rode my bike to work most mornings after that, and I always looked forward to the effect. I’d start out alone, pushing up that shallow grade. Next I’d curl through the corner of Golden Gate Park and into the long green strip of the Panhandle, where I’d pick up a few fellow travelers. And then, the thickening: I would zigzag through the Wiggle, gaining new companions block by block, and emerge onto Market Street in possession of a posse, an impromptu bicycle gang, a protective cohort.

Every day the bikes comprised a new sample of the city: fixed-gears in flat colors, sure, but also tough commuter bikes with plasticky saddle bags and insectlike racing bikes with mud flaps and old Schwinns that made a rickety click-click-click. We would travel together down the slope and span of Market Street, until bikes and their riders began to peel off in ones and twos at 5th Street, at 4th and 3rd, vectoring toward bank towers and start-up lofts. I rarely saw the same people twice.

So the Wiggle is more than a flat path. It’s a community. The Wiggle says: You shouldn’t be riding alone. Here — all of you — stick together.

Today, the Wiggle hides in plain sight. The city recently repainted the way, marking the turns with bright green sigils. You can’t miss them. This is a good thing, just one sign among many of the bicycle’s growing influence in San Francisco. There’s even talk of closing Market Street off to cars entirely; it would be reserved for buses and bikes.

But the path between the hills is still enough of a secret that there is pleasure in its revelation. A friend of mine got a bike recently — a big, boxy cruiser — and upon learning of her admission into the guild, I said to her: You know about the Wiggle, right? Her eyes widened and she shook her head no. Not yet.

Townies welcomes submissions at townies@nytimes.com.

Robin Sloan is the author of the forthcoming novel “Mr. Penumbra’s 24-Hour Bookstore.”