It’s early September on New York’s Rockaway Beach, and the strong winds—aftershocks of Hurricane Harvey—keep most beachgoers away. But not sandcastle artist Calvin Seibert.

He’s sitting on the shore, midway through sculpting the latest of the many whimsical castles he’s made over the course of the summer. This one—whose angled edges and shadowy nooks resemble a Brutalist temple by way of —rises from a plot close to the crashing waves.

I meet Seibert around 4 p.m. in the late-afternoon glow of Beach 67th Street. He’s alone, stationed between two rock jetties. He’s hard to spot at first, dressed in a sort of camouflage: beige pants and hat matching the sand, and a blue button-down blending with the sea.

It’s no surprise that Seibert’s wardrobe has begun to imitate his work. The artist, now 59 years old, has been making sandcastles most of his life. Over the last five years, he’s made the ephemeral structures the focus of his overall art practice, which has also included sculptures forged from cardboard salvaged from the street. “I’ve always made things outdoors from the materials I find around me, so this is sort of a long continuation of that,” Seibert tells me, as he smooths surfaces and adds passageways to today’s castle, his second-to-last of the summer.

Seibert grew up in Vail, Colorado, in the 1960s, when the resort town was growing fast and mired in construction projects. “Everywhere you looked, there were construction and sand piles to play in, and scrap and garbage mounds to pull stuff from,” he remembers. From these leavings, he built treehouses, fantasy worlds, and models of buildings that he’d glimpsed, like the TWA Flight Center at New York’s JFK Airport.

Seibert admits that he hasn’t changed much since those days: “There are pictures of me from back then, and I look exactly the same as I do now. My hands are covered with cement and sand,” he shrugs.

Seibert’s early days playing in sand piles led him to New York, in 1979, to study at the School of Visual Arts. Through the 1980s and ’90s, he explored different mediums, but often found his way back to the beach. “I used to do drawings,” he remembers. “but ultimately I stopped making them, because the light in them was too flat and not atmospheric enough. I had to move on to another way of expressing myself.”

Working en plein air, in places where natural light reflected off the glittering sand and ocean, provided an appealing alternative. In the late 1970s and early ’80s, Seibert drove several times from Colorado to California, where he’d build castles on Laguna Beach and elsewhere. In the early ’80s, he also began taking advantage of the beaches much closer to Manhattan, taking the train out to Jones Beach in between construction gigs, assisting other artists, and making art out of his small, rent-controlled apartment in Chelsea.

For the past several years, Seibert has spent the bulk of his summers on New York’s beaches, building his own unique vision as an architect of modernist sandcastles. Most mornings, between June and early September, he sets off from his apartment in Manhattan around 7:30 in the morning. He travels light, given the scale of the forms he’s about to carve: a sketchbook and tools; buckets for carrying water; and plastic strips with bevelled edges, used to cut and smooth the sand.

Like most other aspects of Seibert’s life, his process is economical. “I do this partly because the main materials I use, sand and water, are free—and there’s a lot of them,” he explains, smiling. “I also live very frugally. No eating out. No movies. No air conditioning. No dog. No car. That’s how I can afford to do this.”

To many artists, Seibert’s approach might seem restricting, but he prefers to keep things simple. “I’ve never wanted to be famous,” he explains. “And showing my work in galleries never gave me any satisfaction.” This past winter, Seibert did buck his own preference, though, and exhibited his sandcastles at Ramiken Crucible on New York’s Lower East Side. For several months, he made them on the gallery floor with construction-grade sand trucked in from a local lumberyard. The show marked a rare occasion that Seibert’s castles were for sale (one went to an unnamed private collector).

Seibert has made money from his sand creations in other ways, too. In May 2016, he was the artist-in-residence at Summit Series, a favorite leadership conference of the tech industry. The gig brought him to Tulum, Mexico, where he built castles on the beach everyday for a week. Hermès also tapped Seibert’s skills for one of the luxury brand’s photo shoots. The trip to took him first to Paris, where he gathered supplies. “On Facebook, I said, ‘I knocked that off my bucket list.…I’m in Paris, shopping for buckets!’” he laughs. From there he headed to Cap Ferret, where he built castles for Hermès models to pose with.

Despite keeping a low profile in the art world, however, Seibert and his sandcastles have garnered quite a fan base during the last several years, helped along by his popular Instagram account. Everyone seems curious about his beach artistry; over the course of our hour-and-a-half conversation, we’re interrupted by passerby, surfers, and a parks-service ranger who all want to watch, ask questions, and marvel at the strange structures emerging from the sand.

Most fans, he admits, will simply express their appreciation (“That’s amazing!”). But others offer more critical takes. The day prior, Seibert had built a towering castle with steep surfaces and vertiginous staircases to nowhere. A passing stranger commented “that it looked like the North Korean nuclear facility,” he recalls. “I thought that was great. That was imaginative. It was kind of brutalist and monstrous, so that idea seemed perfect.”

Seibert’s mind-bending structures have taken many forms—and recall a host of references, from real to fantastical. This summer, one crowd favorite obliquely resembled ’s Guggenheim Museum Bilbao, or a futuristic factory that might produce cyborg parts within its bulbous accretions and angular spires. Another castle, this one cone-shaped and spotted with faceted growths, looked as if it might be the hiding place for a magical talisman.  

And what would his next castle—the final of the season—look like, I wondered? “No idea yet,” he says. “You’ll have to come out to the beach to see.”