If someone ever asks you the same question, be well assured of the answer, “It depends!”. It depends, because that cedar may be as big, tall and old as you want, but if no one has ever declared it as Monumental, it is not.
Yes, it is always the law that rules over everything. And the definition of “Monumental Tree” is only a legal definition. Something for technicians, city administrations, foresters and regional public agencies.
And yet, everybody can at least inquire if a big tree is a Monumental Tree or not, and if it should be protected by the municipality that houses it. Reporting a potential Monumental Tree to the city offices will often push them to conduct a census and update the Monumental Trees database together with the competent regional authorities.
To date (last update: July 2022), the National Italian Monumental Trees Register counts more than 4000 trees . In the Veneto region, there are 244 Monumental Trees, in the Autonomous Province of Trento, 85 and in the Autonomous Province of Bolzano, 40.