The event's organisers said they wanted to draw public attention to the problems experienced by the northeastern city, where the population recently fell below 60,000.
"In Venice, houses cost twice as much as they do on the mainland, and it's too much for the middle class," Pierluigi Tamburrini, of the Venessia.com citizens' group, told AFP.
"We are asking for more action from the city authorities to help residents. We don't want the tourist monoculture we have at the moment -- we have to develop other areas."
A US university used Saturday's gathering of Venetians to collect DNA samples for a project researching the origins of central and western European populations.
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