ROME, JULY 18 -- A spectacular rock concert by Pink Floyd brought the house down at St. Mark's Square in Venice the other night. Now it threatens to bring down the city government. While the show itself was marred by only a few small incidents, its legacy -- mountains of trash, at least one damaged historic monument and dozens of others used as open-air latrines by some 200,000 spectators -- has churned up emotions to an angry froth in the delicate lagoon city. As one city official after another rushed to disavow responsibility for the mess, Venice's mayor, Antonio Casellati, stepped up before a packed public meeting Monday night to concede that the concert had been "a mistake." But he claimed his government had come under "unusual pressure" from state-run television -- which had sold the broadcast rights to more than a dozen countries -- and other political interest groups to let the show go on. "There were many contacts and contracts in this whole affair," he said. But Casellati's implacable Venetian audience wanted blood. "No excuses," they howled, drowning Casellati out several times with whistles and insults during his half-hour mea culpa. "Fools, scoundrels," cried others. "Resign, resign, you've turned Venice into a toilet." The Republican mayor, facing a motion by the opposition Christian Democrats to step down, said he would put the resignation of his coalition government to a vote of confidence by the city council, which Italian newspapers interpreted as "almost resigning." Casellati urged council members, in the process of deciding his fate, to devise some "precise and unavoidable rules so this city will never again be exposed to these kinds of risks." To many ears, the libretto of this Venetian opera sounded familiar. Scandals erupt frequently in Italy, only to die down almost as quickly, often unresolved. Many involve legitimate questions that are rarely, if ever, answered: In this case, should a unique and fragile open-air museum like Venice be used for mass entertainment? Proponents of the concert pointed out that Pink Floyd, which played from a floating stand anchored off St. Mark's Square, agreed to turn down the band's amplification from 100 to 60 decibels and that the young fans acted with remarkable respect for their historic surroundings. It could have been worse, they added. "Let's not declare a holy war," intoned Deputy Premier Gianni De Michelis, a Venetian whose Socialist Party was among those who pushed for the concert. "After all, nothing particularly serious happened in relation to the large mass of people." A like-minded Venetian, Vittorio Sgarbi, blamed the furor on what he called "complaining Cassandras," saying: "Venice was always a city for spectacles ... this is all ridiculous. There wasn't even a death. A little trash and all will be forgotten in three days." A little trash? According to city officials, 300 tons of garbage and 500 cubic meters of empty cans and bottles were left behind in St. Mark's Square after Saturday night's concert. Television footage the next day showed Venice's famous pigeons picking their way through a thick carpet of refuse over the historic piazza -- not much a subject, right now, for picture postcards. In addition, because of the lack of adequate sanitary facilities, hundreds of fans apparently were forced to relieve themselves where they could, leaving a distinct odor that added to the loud complaints of the city's denizens. Although an architectural team had warned the government that vibrations from the amplified rock music might cause widespread damage to the structures and facades of the adjoining cathedral and Doges' Palace, a preliminary survey yesterday showed only a hunk of marble from a group of statues on the palace facade known as "The Judgment of Solomon" had been displaced by the dangerous vibrations. But this was more than enough for the concert's many critics. Former Rome mayor Renato Nicolini, observing that a 1960s Rolling Stones concert in the same square caused it to sink further into the lagoon marshes, said the show never should have been staged in a city that flooding, the churning wakes from motorboats and various other environmental problems have already rendered extremely delicate. "This wasn't a cultural event," he charged, "but a great commercial enterprise promoted by television and the record industry." The environmentalist group Italia Nostra (Our Italy) apparently agreed, filing a formal complaint with a Venetian magistrate alleging misconduct and corruption of the city's public officials in allowing the spectacle to take place. Yet skepticism reigned among many critics about whether the brouhaha would produce any concrete results, or set positive precedents for the future in a country often subject to such debates involving its great cultural heritage and the risks of modern times. Comparing the Venice mega-flap with the similar mishandling of the algae crisis now plaguing the Adriatic Coast, La Stampa columnist Lietta Tornabuoni found the situation symptomatic of a political class that "can't govern, can't administrate, can't decide, can't assume responsibility, can't plan and can't provide."