The still-expanding probe involves alleged kickbacks and bribes during previous mayoral administrations.
Politicians from the center-left and center-right have been indicted.
The alleged ringleader is Massimo Carminati, who has past links to far-right extremism. His lawyer, Gosue' Bruno Naso, scoffed at allegations violence was used to win contracts.
He told reporters before the trial began today there is corruption in all cities and that "this country is morally rotten."
