Venice's past resonates into the present in more than just the shimmer of the city's beauty.
As strange as it was to see the romance and serenity of the piazza San Marco violated last May by masked, gun-toting terroristi, the incident was connected, even if a bit bizarrely, to Venice's enduring political past as a great city-state.
The eight gunmen who seized the piazza's bell tower were fringe members of a separatist party, the Northern League, which aims to transform northern Italy into a breakaway nation.
The separatists hoped to exploit the bicentennial of a historic event: the fall of the Republic of Venice to Napoleon in May of 1797.
But even then, the transition was remarkably peaceful. The Great Council - the body of noblemen who governed the city - voted itself out of existence, and the city and its sprawling empire were transferred to Napoleon without a shot being fired.
Today, Venice is best known as a relic of earlier times. Other great cities from Italy's past - Rome and Florence, for example - have been dramatically altered by the modern age.
Venice, by contrast, remains a city built to a human scale. There are no cars, skyscrapers, or malls. Its churches and museums are filled with works by Bellini, Titian, Veronese, and Tiepolo. Its palaces are paradoxes of the stately and the whimsical, its canals and narrow passageways mysterious mazes.
But as intriguing as the city's physical beauty is the city's political past - a lesson about the enduring qualities of stability.
In 1297, exactly 500 years before the fall of the republic, the Venetian constitution began to take shape.
It is a constitution easily recognizable to Americans. At its base was a Great Council, consisting of some 2,000 noblemen. This was Venice's sovereign body, from which the Senate and the councilors of state were elected. At its summit was the doge, an elder Venetian aristocrat elected to office for life, whose power was held in check by a vast array of institutions, including the great law courts of the republic.
Venice's history is above all the history of political stability. Our own republic is now less than half the age of the Venetian Republic at its demise.
What lessons does Venice have to teach us?
The first lesson - understood by such architects of our own Constitution as John Adams, who knew the Venetian model well - is that republics are strongest when their citizens place their confidence in laws and institutions rather than in the political promises of individuals.
The second lesson is that republics thrive when they remain open to the world.
As a center of trade, Venice was polyglot and managed to remain relatively tolerant even in periods of intolerance that elsewhere divided Europeans from one another and from members of other cultures.
Jews and Muslims, Greek Orthodox and German Lutherans, as well as numerous other foreigners had little difficulty making their home in Catholic Venice.
The third lesson is that republics are fragile - not to be taken for granted, butcontinually revitalized.
In the age of the Enlightenment, with its new ideals of popular sovereignty, the Venetian Republic, still based purely on the idea of aristocratic sovereignty, no longer stood at the forefront of models of republican freedom.
But even though the Venetian Republic may have fallen 200 years ago, its lessons still matter.
Our own polity, for example, would do well to avoid the present cult of personality that threatens to render our laws and our institutions of secondary importance. Tolerance, too - especially in an age of "moral" majorities and growing anti-immigration sentiment - must remain a central value of American political and cultural life if we intend to endure as a center of commerce.
Finally, we should not envision our society as static but as flexible, able to adapt to as well as influence the changes in global politics.
Random acts of terrorism in the US will do no more to restore an America that never existed in the first place than the tragicomic occupation of the bell tower in St. Mark's Square did to bring back the Venetian Republic.
By contrast, a clear understanding of history can help preserve and improve the best of our accomplishments.
Particular republics inevitably decline and fall.
But, as the examples of Venice and other ancient and modern republics make clear, the spirit of a republic can endure far into the future.
Venice, like Rome, is an eternal city.
* John Martin and Dennis Romano, professors of history at Trinity University, in San Antonio, Texas, and Syracuse University, in Syracuse, New York, respectively. They are organizers of the conference "Venice Reconsidered: Venetian History and Civilization, 1297-1797," being held this weekend at Syracuse University.