To an architectural enthusiast, it’s a Modernist masterpiece. To its owner, Michael Harris Spector, it’s a sculpture. His wife, Joan, thinks of it as,  well,  a spaceship.

That was her impression one evening 17 years ago when her husband drove her to a secluded section of Old Westbury to see the house known as the White Castle.

“It was very dark, and there were no streetlamps,” she says. “Light was streaming out of the atrium, and it looked like a spaceship had just landed.”

Designed by Richard Meier, an architect known internationally for his white-themed projects, the house turned out to be more down-to-Earth. Now, after years of enjoying its brash whiteness, filling it with artwork and entertaining their large family, the owners say they are hoping to pass it along to someone who will appreciate it as much as they do.

“Everywhere you look there is light and simplicity,” says Spector, who is asking $8.8 million for the home.

He and Joan are moving to the luxury condominium complex known as the The Ritz-Carlton Residences in North Hills. “I don’t think I could ever sell it to someone who just wanted to bury their money in it.”

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His connection to the residence dates back to 1970, when it was commissioned by an eye surgeon who wanted a home with a modern motif. Spector, the founder of an award-winning architectural firm responsible for many of Long Island’s most notable buildings, such as RXR Plaza (formerly EAB Plaza, near the Nassau Coliseum), submitted plans. So did Meier, probably best known for designing the Getty Center in Los Angeles. It was a genial competition.

“He won,” Spector says, laughing.

Spector moved on to other projects (including the 11-story federal courthouse and office building in Central Islip, designed by Meier, where the two became good friends), and forgot about the house until years later when he read it was for sale. There was one problem. His wife told him after their nighttime tour that she couldn’t possibly live there. The area was too dark, the grounds unkempt and the home a general mess. He promised to bring it back to its original condition and give her a garden, too.

While considering it over the next few days, she noticed how sad he was about possibly losing the home to another buyer.

“I said, ‘You really want this house, don’t you?’ ” says Joan, 75, a retired clinical psychologist. She agreed to the move and he arranged to buy it the next day.

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The yearlong renovation opened up a series of rooms upstairs that were part of the original design and modernized the kitchen. Spector landscaped the grounds, put in the promised garden and began placing his own metal sculptures in spots throughout the nearly five-acre lot.

The 11,000-square-foot home includes six bedrooms, five bathrooms and two half-baths, a great room, living room, formal dining room, eat-in kitchen, gym and an observation deck. Spector’s second-floor design studio at the rear of the house can be reached by a long walkway next to the in-ground pool. He commandeered the pool house for his sculpture workshop. There is a tennis court behind the house.

The home’s interior is a virtual canvas that the owner has splashed with colorful artwork. This ranges from a giant painting by Sam Francis to an even larger two-story creation on another wall by Gilbert & George, known for their vivid graphic, photo-based artwork. A red sculpture that looks like a shuttlecock by Anish Kapoor, who did the giant chrome “Cloud Gate” (the bean) in Chicago, sits above the fireplace.

“The interior is just as beautiful without it,” says Spector, who is taking his collection with him.

Nothing about the home is conventional, starting with the entrance, an 8-foot blue door that rotates on a pivot. Spector says this was a concept borrowed from Le Corbusier, a legendary French-Swiss architect and Modernist pioneer who influenced Meier, among other architects.

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Meier has stated that the structure’s “circulation system,” which includes the ramps and circular stairs, was a major design theme for the home. The eye-catching ramps, which are visible through the glass atrium, provide access to the three upstairs floors and are long enough for an aerobic workout.

Spector pauses at the middle ramp and faces the flood of sunshine.

“Sometimes, I just come out here and soak it up,” the 77-year-old architect says.

The ramps also have been a temptation for his nine grandchildren, who saw the arrangement as a skateboard lure. Spector placed one of his steel sculptures at the end of one ramp as a deterrent to keep them from plowing through a window at the bottom.

Obviously, the home’s dominant feature is its pervasive whiteness. Meier has been quoted as saying, “The whiteness of white is never just white; it is almost always transformed by light and that which is changing; the sky, the clouds, the sun and the moon.”

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Spector, who also has a fascination with white and who gave the house its name, agrees. He especially appreciates that the outside is visible from everywhere in the house, with many of the rooms having floor-to-ceiling windows.

“Sun, shade, shadow — it’s everywhere,” he says.

OTHER LI BUILDINGS BY THE ARCHITECT

Other Richard Meier projects on Long Island include:

The Fire Island House: Situated in Fair Harbor, the home has two-story-high glass walls on three sides, a floating stairway connecting the floors and other elements to maximize natural light and views of the bay.

The Saltzman House: The site of this East Hampton home, which has a cubic composition, was elevated to allow views of the sea, the coast and Montauk point. The ocean view is revealed as you move upward in the home.

U.S. District Courthouse in Islip: Visitors enter the courthouse, which has panoramic views of both the Great South Bay and the Atlantic Ocean, through a nine-story rotunda in the form of an opaque white metal cone. Both wings of the building connect to a central 11-story atrium.