A Very Brief History of Venice

Venice was just a lagoon but in the Fifth Century invaders from the north caused people from the nearby mainland to flee to a place where ship-less Huns were not likely to attack and by the Eighth Century Venice had an elected government and soon was strong enough to repel Charlemagne and in 828 acquired relics of Saint Mark (symbol: Lion)

for its basilica and over the next few centuries became a center of trade (Marco Polo et al.) and a military power, dominating the seas, assisting in crusades and generally having its way until about the Fifteenth Century when things started going downhill (a figure of speech, as lagoons tend not to be hilly), not only with other countries opening new sea routes but also a reoccurrence of the Black Death and finally with Napoleon showing up in 1797, ending over a thousand years of Venetian independence; however, in the following century after a lengthy Austrian occupation Venice regained its independence and became part of modern Italy, but not before becoming popular as a tourist destination and if global warming gets out of hand it may well go back to being just a lagoon.
Ciao.