FIFTH AVENUE CURVES

LAST month's gala reopening of Frank Lloyd Wright's Guggenheim Museum, which was closed 2 1/2 years for restoration and expansion, is undoubtedly the art and architecture event of the year. This is to be expected, for this extraordinary and prepossessing structure, the last by America's greatest architect, and his only in New York City, seems destined always to fascinate.

Commissioned in 1942 by copper-mining heir and modern-art collector Solomon R. Guggenheim, and designed and redesigned for many years, the building provoked debate well before its 1959 completion. (It opened in October 1959, six months after Wright's death at age 91.) At the core of the controversy were such basics as form and function. Wright's fantastic spiral, his cantilevered "sea snail," seemed to many observers a wildly intemperate intrusion on staid Fifth Avenue, monstrous poured-concrete proof th at the creator of the prairie house did indeed despise the city. In critic Herbert Muschamp's words, "... its brazen exterior undulated like a fat fille de joie importuning passersby on the city's most solemnly decorous street."

Even more questionable than the siting of the building, to many, was its appropriateness as a museum. In 1956 a group of major New York artists, including Franz Kline, Willem de Kooning, and Robert Motherwell, signed a petition protesting the design. They argued that the building, with its tilted walls, sloping floors, and relentless 3/4-mile ramp, was "not suitable for a sympathetic display of painting and sculpture." Over the years the experience of thousands of gallerygoers has proved the artists' fea rs well-founded. Although Wright rationalized his great rotunda by arguing, for instance, that the outward slope of its walls approximated the tilt of an artist's easel, his interest plainly lay not in the building's future contents but in its forms and spaces. (To the protesting artists he disdainfully replied, "... you understand all too little of the nature of the mother art - architecture.")

Wright had, in fact, long been fascinated with circular and spiral forms, with the ideas of plasticity and continuity, and he sought obsessively to create spaces that would embody what he called, with characteristic eloquence, "the continual becoming." As early as 1925 he designed his first spiral, an unbuilt planetarium project in Maryland; and in the late '40s he incorporated a two-level spiral in the V.C. Morris store in San Francisco. As architect Peter Blake wrote of the Guggenheim, "The fact is, qu ite simply, that Wright just had to build one great, wonderful spiral before he died, and he managed to sell the Guggenheim Foundation on the idea that it would make a good museum." Little wonder, then, that the building has rarely showcased any art so well as its architect's. In a recent New York Review of Books, art historian John Richardson puts the case succinctly. "Across Wright's beautiful rotunda, paintings have a way of looking like posters or pimples, sculptures from above like unclaimed luggage."

Over the decades the controversy has, predictably, cooled as the building's eccentricities have become familiar. Still, the Guggenheim has continued to pose an intriguing contradiction: Although ungainly in its urban context, ill-suited to its use, it is nonetheless a great building, impossible to dismiss. This is a contradiction that the current restoration and the new 10-story addition, by the well-respected New York architects Gwathmey Siegel & Associates, serves to underscore, even institutionalize. Their intelligent and respectful work has made the 33-year-old building look better and more imposing than ever, while improving it only marginally as a venue for modern art.

The art-display improvements are attributable to extensive technical upgrading (improved artificial and natural lighting, climate control, glazing, etc.) and to the creation of several flat-floored and straight-walled galleries. Wright's small rotunda, which had been partitioned into wedge-shaped offices, is now mostly exhibit space, housing a collection of late-19th and early-20th century European art. Skylit, like the large rotunda, it contains a lovely sequence of spaces, with a delightful new roof-to p sculpture terrace. Several good new galleries - rectangular, high-ceilinged rooms that can accommodate big-scale contemporary art - are located on the lower floors of the Gwathmey Siegel addition.

This addition, whose 31,000 square feet includes offices as well as galleries, is a scaled-back version of the firm's 1985 proposal. That design, which cantilevered menacingly over the Wright building, became quite notorious, exciting what Guggenheim director Thomas Krens tactfully calls a "spirited public debate." As redesigned and built, the limestone-clad tower is a handsome backdrop that neither detracts nor competes with the original museum. In a sense, Gwathmey Siegel has discovered what many paint ers and sculptors have learned - that to take on Frank Lloyd Wright is a losing game.

For all their excellence, the new galleries and addition are inevitably ancillary to the great spiral, which has been beautifully restored. Here various insensitive alterations have been, in Charles Gwathmey's term, "rectified." The ramp's top level, walled in early on and used for storage, has been opened; visitors will now have the satisfaction of completing their circular journey. The perimeter-strip skylights, boarded up years ago, have been uncovered. Exterior concrete and interior plaster surfaces have been refinished, making the building's shapes and edges crisp and clean.

While the restoration has clarified the sensuous beauty of the space - "the most visionary and memorable in the 20th-century architecture," opined Mr. Gwathmey at the press preview - it has also highlighted the building's self-sufficiency, its lack of need for painting and sculpture. And, cleverly, the Guggenheim's curators have dodged this issue by giving over the entire large rotunda to a single site-specific work by Minimalist Dan Flavin. Mr. Flavin, whose medium is neon, has placed a 100-foot-high co lumn of pink neon tubes in the rotunda's center, and lit the walls in shades of pink and green. The work intensifies the effect of the space, while precluding the usual viewer complaints (poor sightlines, sloped walls, etc.)

Future shows will reveal more of the restoration's strengths and shortcomings. In any event, the Guggenheim Foundation plans to gain a good deal more space to display its collection. (Before the current expansion, 3 percent of its holdings could be shown; now the figure is 6 percent.)

Ambitious in its own right, the Fifth Avenue restoration-expansion is only one item in a grand, trans-Atlantic development program, for which the foundation has hired several architects of international reputation. Just completed and opened to the public is the museum's beachhead in downtown Manhattan. Occupying three renovated floors of an 1882 commercial building, the Guggenheim in Soho was designed by Japanese architect Arata Isozaki. Still on the drawing boards are the Guggenheim in Bilbao, Spain, by

California architect Frank Gehry, and the Guggenheim in Salzburg, Austria, by that country's Hans Hollein. Still in negotiation is the Guggenheim in a former factory complex in North Adams, Mass.

The realization of these big plans will take big sums. To pay for recent construction, for example, the foundation issued nearly $55 million in tax-exempt bonds, and some art-world observers are worried that the museum may be forced to use pieces from its permanent collection as collateral. Although Krens denied this "on the record," skepticism lingers. Indeed, critics have lately belittled the proposed outposts as "museum franchises" and "branch offices" - unwelcome evidence of how art has become big bu siness.

Money matters aside, all this architectural activity is exciting. Certainly it will be interesting to see whether future Guggenheims match the standard set by the first. In the meantime, museum officials have come to terms with their Frank Lloyd Wright, which they now describe as "one of the greatest masterpieces in the museum's collection." This seems a fitting assessment of the last legacy of the man who was, as Lewis Mumford wrote, "one of the most creative architectural geniuses of all time."