NEW YORK (NYT NEWS SERVICE ).- Frank Lloyd Wright’s Solomon R. Guggenheim Museum is still a shock on Fifth Avenue. The architecture declines to fade into the background or get old, never mind the building turns 60 this month.

Happy birthday to one of modern architecture’s transcendent achievements! Its spiral ramp has defeated generations of curators trying to figure out how to install exhibitions on it. The building has gone through ham-fisted additions, hostile restorations, lousy paint jobs and too many bad imitations to count.

But it endures everything, a testament to what critic Ada Louise Huxtable once called its “unified space and structure.”

Neither Wright nor the man who commissioned him to design the building, Solomon R. Guggenheim, saw it finished. Guggenheim had died a decade earlier, Wright shortly before the building opened. He was 91.

The two of them cooked up a plan for the museum back in the mid-1940s; it was to be a purpose-built container for Guggenheim’s private collection of nonobjective art. Under the spell of a German baroness and abstract painter named Hilla Rebay, Guggenheim had amassed a vast collection of Kandinskys and Arps — and Rebays — which, Rebay had persuaded Guggenheim could conjure up a new, elevated reality.

Such lofty art naturally demanded a home befitting its spiritual potential — a temple, in effect, that was itself pure, abstract and uplifting. To an evangelist and egomaniac like Wright, the assignment seemed karmic.

It also partly explains why the museum lacked traditional galleries and made little allowance for the sort of back-of-house accommodations museums typically need. There was next to no room in the plan for storage, although room was allotted for two apartments, one for Solomon Guggenheim, the other for Rebay.

Then Guggenheim died. His nephew took over the project, and for years construction stalled because of rising costs and material shortages after the war. In addition, Wright’s design violated all sorts of New York building codes, so the Guggenheim couldn’t get a permit until Wright reached out for some help. Robert Moses, the city’s all-powerful planning czar, while he had no love for modern art or Wright’s architecture, was related to Wright by marriage. Magically, the museum got its permits.

Meanwhile, the Guggenheim family after Solomon’s death had decided the collection should no longer stick to just nonobjective art and that Rebay had to go. So she was fired as director.

Hired in her stead was James Johnson Sweeney, formerly of the Museum of Modern Art, who set about undoing much of what Wright wanted, switching out the architect’s soft, buff-colored walls for stark white ones, driving stakes into the ramp to hang pictures instead of going with Wright’s easel-like ledges and installing artificial lights at the top of the ramp, where Wright favored natural daylight and shadows. Sweeney fought with Wright constantly. He then survived Wright, who died six months before Sweeney helped cut the ribbon at the museum’s opening. But Wright’s architecture got the last word.

In photographs, you can see Wright wearing his porkpie hat in the half-built shell of the museum, contemplating plans with the construction crew. For good reason, he shared credit on the Guggenheim’s cornerstone with the chief builder, George N. Cohen. The project pushed midcentury engineering to the limits. What looks today like a prophecy of late-20th century computer-generated design could only be achieved back then with reinforced concrete, poured into wooden molds. All those structural curves involved lots of eyeballing, crossed fingers and educated guesswork.

What resulted is a landmark of sculptural architecture: an inverted ziggurat, with stacked volumes rising from a floating, rounded pedestal, forming a pair of rotundas. The passage Wright choreographed from the museum’s low, compressed entrance into the soaring main rotunda is still one of the city’s great thrills. Wright at one point imagined the building in pink and even bringing Central Park across Fifth Avenue, creating a greensward between the museum’s big and little rotundas. He loved nature and wide open spaces. But he wasn’t big on New York, to which the museum conspicuously closes itself off.

That said, the Guggenheim is a kind of city square. Its ramp, circling around the rotunda, echoed earlier, inward-facing buildings the architect had devised with balconies around central spaces, among them the Larkin and Johnson Wax buildings. The Guggenheim extends the concept, the museum spiral unspooling in a way that can put a visitor who walks up or down the ramp in mind of strolling around a city, glimpsing strangers across the street, gazing at shop windows, deciphering snippets of passing conversation, feeling the hum of public space, marveling at the shifting, vertiginous views.

It’s Wright’s control-freak version of urbanism.

Among much else, it inspired Frank Gehry’s enormous Guggenheim in Bilbao. Today, when art museums and galleries seem only to keep getting bigger, Wright’s Guggenheim by contrast, even with its expansions, remains a human-scaled place to contemplate art, the architecture exalting and intimate, almost domestic.

Sure, the architecture competes for your attention with the art because Wright’s buildings are on some level always, ultimately, about Wright. But there is no more moving or inspired space to see an exhibition when the ramp is sympathetically installed.

At 60, the museum is still going strong, a dowager disrupter.

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