The Montauk Point Lighthouse on Long Island is the oldest in New York. (Gregory Payan/AP)

If you grow up on Long Island, there are certain inevitabilities. Manhattan will always be the city; traffic will always crawl. And if it’s summer, you’ll always, always end up at the beach.

I haven’t lived here for nearly a decade. But I’m back for the weekend, and here I am (after far too long in a bumper-to-bumper jam), sitting on a patch of rocky sand, curling my toes as the Atlantic’s waves crash around my ankles.

But this time, there isn’t an umbrella or a bikini in sight. There’s dirt streaked across my cheeks, and I’m wearing a sweatshirt and sneakers.

I’ve returned to the island’s South Fork (the 45-mile-long bottom “fin” of this fish-shaped suburban enclave) to explore one of its less-celebrated resources: the hikes and nature preserves.

Details: Getting to Long Island

The options are bountiful. Michael Bottini, a writer and naturalist focused on Long Island’s East End, estimates that there are at least 250 miles of hiking trails on the South Fork. Some wind their way through beach dunes, others through lush forests or scraggly seawater plants. More than a few start (or end) at a lighthouse.

Which is where my mom and I start, after an hour-long crawl on the South Fork’s two-lane highway. (Summer traffic can get so bad that many regular visitors opt for the train or the Jitney, the bus whose fictional doppelganger has transported the characters of “Girls,” “Gossip Girl” and “Sex and the City.”) We’re on the hunt for the Cedar Island Lighthouse, a two-story structure that looks like nothing so much as a haunted Victorian sand castle.

The building, which once guided whaling ships to Sag Harbor, has a creepy history. According to local legend, its 19th-century keeper, Charles Mulford, was obsessed with peg legs and allegedly bought up and squirreled away every one in town. A 1974 fire charred his room full of prosthetics.

In 1934, the lighthouse was purchased by Phelan Beale, the husband of Grey Gardens’s Edith Beale. It was passed to the county park system in the 1960s.

The lighthouse stands at the tip of a mile-long peninsula in Cedar Point County Park, a 607-acre space rife with campgrounds and nature walks. It also has a general store. To get there, we amble along a stretch of rocky beach, which offers stunning views of Gardiners Bay (often swimming with sailboats) and Shelter Island.

Afterward, we poke around East Hampton, one of Long Island’s poshest Zip codes. Jerry Seinfeld and Martha Stewart have mansions here.

But we resist the temptation to eat at one of the many cute cafes, ice cream shops or seafood shacks. Instead, we drive on to the Lobster Roll for lunch. With an American flag out front and red, white and blue awnings, the joint calls out to travelers on the highway with a giant “Lunch” sign in big blue letters.

Inside, a waitress guides us to a table with two paper placemats that tout famous visitors (Sarah Jessica Parker and Richard Nixon among them). We skip the fried puffer fish and opt instead for cold lobster salad sandwiches (invented here, according to the American Dictionary of Food and Drink). They come out fast, with two ice-cream-scoop-size servings of lobster, mayonnaise and celery pillowed atop a buttery roll.

Next, we stop at Hither Hills State Park. There’s little greenery here — instead, campers and walkers visit the moonlike sand dunes to view the ocean. Tree stumps jut out of the sand, tombstones honoring the once-lush forest.

We drive about 20 more minutes to Camp Hero State Park, on Long Island’s easternmost tip. The park has an unlikely history: It began as a Revolutionary War battle site, and its first lighthouse (built in 1792) was intended mostly as a way to keep track of potential British invaders. During World War II, the Army, worried about encroaching German ­U-boats, built docks, seaplane hangars and barracks. Even today, hikers can spy defunct radio towers and former gun emplacements.

Beyond the military history, though, is a magical path through dense forests. The winding trail, barely wide enough for one person, is overgrown on both sides with brush and prickly bushes. On a couple of occasions, walkers venture over rickety wooden bridges.

But every once in a while, the path opens onto a grassy bluff overlooking the ocean, with spectacular cliffside views of water as far as the eye can see.

I look in vain for evidence of the seals that make their home here in the winter. Once, I spy a sign that shows what I think is seals bouncing a toy on their noses. On closer inspection, I realize that it’s a person falling off a cliff, warning visitors to stay away from the edge.

The views come reliably, and eventually the trail spills out onto a rocky beach, overlooked by the Montauk Point Lighthouse. It’s the oldest lighthouse in the state, originally authorized by George Washington. The museum inside boasts, among other items, a letter signed by the first president himself.

Afterward, we pop into the Montauk Bake Shoppe for sustenance. If East Hampton is a posh 20-something, Montauk is the cousin in jean shorts. Instead of B&Bs, there are motels. No flowering trees dot islands in the middle of the road; one-story souvenir shops and fish stores run almost uninterrupted down Main Street.

In between cookies shaped like lobsters and frothy pink cupcakes, we find a plate of jelly-filled croissants. The shop clerk tells me that her father invented them in the ’80s, and that in the summer, they’re almost always sold out.

“They were the inspiration for the cronut,” she claims proudly.

After our snack, we’re back in traffic, watching sports cars and minivans pull past on their way to vacation homes for an early start to the summer. If they spend all weekend on the beach, I’d be a little jealous. But I’d also think that they don’t know what they’re missing.

Erickson is an assistant editor with The Washington Post.