A Bluffer's History of Venice.
In 568 as the Lombard barbarians swept through northern Italy the refugees who fled before them began to congregate in the Marshes of the Po estuary. The settlement they made there was eventually to become the City of Venice.
Between the eight and twelfth century Venice gradually emerged from under the protective wing of the Latter day Eastern Roman Empire known as Byzantium. As Byzantine power waned Venice took advantage of her geographical command of the Adriatic and cashed in with aplomb. The riches that rolled in through her trading routes in turn funded her Naval dominance.
All these factors made Venice an ideal launch pad for the Crusaders eager to plunder and re-conquer the Muslim near-east and it was when the Fourth Crusade took Constantinople in 1204 that Venice became an Empire in it's own right. Venetian territory spread down the Greek coast and it's islands and expanded around the city into mainland Europe. The Crusades allowed Venice to capitalise on the fall of Constantinople and the spoils of that war. Among many other treasures, the crusaders brought home the Winged Lion of Saint Mark, symbol of Venice. It now stands in St Marks Square.
The Venice of romantic fantasy was the Venice of the Eighteenth Century. This was the Venice of fine art and opera, of commedia dell arte plays and carnival masks. In 1797 Napoleon's Invasion put an end to the last century of Venetian decline and it was in decline that Venice was at it's most excessive. Competition from the English and Dutch trading fleets had pulled the rug of economic supremacy from under glorious Venice and it seemed there was nothing left to do but dance.
It was at this time that the Carnival could last from the day after Christmas till the day before Easter. That is to say some six to eight weeks of solid partying reminiscent of Nero fiddling while Rome burned.