The city was founded as a result of the influx of refugees into the marshes of
the Po estuary following the invasion of Northern Italy by the
Lombards in 568. At first an outpost of Byzantine civilization, as
the community developed an anti-Eastern character emerged, leading to the
growth of autonomy and eventual independence. Venice was a city state
(an Italian thalassocracy or Repubblica Marinara - the other three were Genoa, Pisa, and Amalfi). The chief executives were called Doge (duke), and, theoretically, held their elective office for life. In practice a number of Doges were forced to resign the office and retire into monastic seclusion by pressure from their oligarchical peers when they were felt to have been discredited by perceived political failure. At the height of its power, Venice controlled much of the coastal territory along the Adriatic, most of the islands in the Aegean, including Crete, and was a major power-broker in the Near East. The territory of the Republic on the Italian mainland extended across Lake Garda as far west as the River Adda. By the standards of the time, Venice's stewardship of its mainland territories was enlightened and the citizens of such towns as Bergamo, Brescia and Verona rallied to the defence of Venetian sovereignty when it was threatened by invaders.
Venetian ambassadors sent secret reports about the politics and rumours of European courts, these supply fascinating information to modern historians.
Venice in true colours
Venice and surroundings in false colour, from TERRA satellite. The picture is oriented correctly (north at the top).