See The Invention of Venice for before AD 568.
Through the tinted Venice glass of the Republic’s later historians, this early period was a golden age. One chronicler called the Venetians
a lowly people, who esteemed mercy and innocence, and above all religion, rather than riches. They affected not to clothe themselves with ornaments, or to seek honours, but when need was, they answered to the call.
The towns scattered across the islands were as yet only wood and thatch, interspersed with gardens, each house with its little boat ‘tied to posts before their doors like horses on the mainland’.
Images by Mongolo1984, Netzach, Creative Commons License, PD Art, Web Gallery of Ar