Futurism on display. Sleepy, elegant Venice was in for a shock. The Futurists wanted `an industrial and military Venice,' or so they said in leaflets dropped into St. Mark's Square from the Clock Tower. Now the city they attacked commemorates them -- in an 18th century palazzo.

`WE repudiate ancient Venice. . .!'' cried the Italian Futurists in 1910. To this noisy and revolutionary band of artists and poets, the decrepit Old Lady of the Adriatic represented everything they wanted to destroy.

Venice represented museums, libraries, and academies. To the Futurists these were ``graveyards.'' It epitomized the heavy dust of ``professors, archaeologists, guides, . . . antiquarians, . . . second-hand dealers,'' spread all over Italy. It was a dust that the forward-looking Futurists would sweep away. Venice represented, above all, the ``nostalgic dream'' of the Past. The Futurists wanted instead to ``prepare the birth of an industrial and military Venice.''

It seems they underestimated the staying power of nostalgia. ``Pass'e-ist'' Venice is still going strong, more protected and popular than ever.

So it is not without a certain conscious irony that the city is hosting the most extravagant and thorough exhibition ever devoted to the Futurists. The irony is compounded by the housing of this magnificent show in an 18th century Venetian palazzo of considerable grace and grandeur.

The Palazzo Grassi has just been restored and adapted, under the auspices of the Fiat organization, with notable respect and care. (It is worth a visit on its own account.) And this mammoth exhibition, ``Futurismo e Futurismi'' (Futurism and Futurisms), to Oct. 12, is certainly evidence of a serious commitment to its use as a cultural center. The exhibition tries to cover every aspect of its subject from origins to international dissemination, and it has what must be the largest, heaviest catalog in existence.

Futurism itself belongs to the past. It peaked, as a movement, between 1910 and 1918. Its aims were newness at virtually any price. Change, speed, industry, dynamism, energy, and youth were its slogans; the manifesto, its primary tool.

It was promoted with well-organized determination by its originator, the poet Filippo Tommaso Marinetti, as a deliberate Italian challenge to the avant-garde in Paris. ``A racing car,'' he declared in his first manifesto, ``is more beautiful than the `Victory of Samothrace' :'' aggressive, confident words, particularly as they predated any evidence of Futurist art, architecture, poetry, theater, or music to prove his point. These soon followed, however, and it is Italian Futurist art that is the meat of this show. Splendidly represented here, the paintings of Carra, Russolo, Boccioni, Severini, and above all Balla are the lasting evidence of Futurism's contribution. And one must not forget the visionary, prophetic architecture conceived by Sant'Elia.

It has to be admitted that Marinetti's excited manifestos are refreshing, for all his absurd anarchism and even his glorification of war, which is now distinctly pass'e. (Today we find it impossible to be so splendidly, naively sweeping about the necessity of newness. In some ways this is a pity.) But the Futurist movement was more than provocative rhetoric. These Italian artists really were stimulated by Marinetti. They were experimental, heroic, optimistic, and rather over-sure of their importance. More interested in movement for its own sake than the Paris-based cubists, their way of fragmenting the visible, of exploring multiple aspects of their subject-matter, was still greatly in debt to the cubists.

This show also indicates the awareness that they must have had of earlier photographic studies, which suggested to them the possibility of representing movement in painting by repetitive but developing forms. Balla's running girl with many feet, his ``Rhythm of the Violinist,'' and his sausage dog with a blur of feet and multiple tails show the charming initial results of this interest. His studies for and final version of a painting -- capturing the dynamics, light, speed, and noise of a fast-moving car -- mark the notable sophistication that he achieved by his ability to pursue a new idea right through to its logical essence.

Though a deal of trouble has been taken in this exhibition to show how Futurism percolated throughout the world -- from Argentina to Belgium, from France to the United States, in Britain, Japan, Germany, the Soviet Union, and many other countries -- the Italians still top the lot.

The Italian Futurists' activities in such everyday areas as furniture, toys, and clothes is revealing. Again Balla is the most inventive, and also the most fun. His designs for clothing, some actually made, are immensely colorful and bold.

If Venice still stands as a monument to the beauty of the past, these cheery garments certainly prophesied the bright clothes of the tourists surging through her narrow streets in 1986. In some respects, at least, Futurism is upon us.