Granfondos are so new that I don't think anyone has really pulled together a history, and not definitively worked out which was first.
Nove Colli was first run as "1st AUDAX amateur cycling of Social Gran Fondo" in 1971. The Fausto Coppi Cycling Club in Cesenatico set out at 5am 20th May to cover a 200km course.
Haven't heard of an older Italian Gran Fondo. The Maratona d'les Dolomites by comparison started in 1987.
The oldest French cyclosportive is the Marmotte which started in 1982. Interesting that it calls itself a Granfondo rather than a "cyclosportif".
The South Africa Pick 'n' Pay Cape Argus Cycle Tour first ran in September 1978.
The Vatternrundan (300km around a Swedish lake) first happened in 1966. Though its not a mass start and comes from a different background - started by a doctor wanting to study the effects of endurance training.
The story behind the Nove Colli is that club members had participated in an "Alpine Patent" in Switzerland (can't find anything much on Swiss "Patents" - they look to be set mountainous cycle courses and I guess take place on particulat days) and decided to create an "Appennine Patent" - the Nove Colli.
Also, having "Audax" in the title of the first Nove Colli gives an indication of another tradition - the Italians created Audax events way back with the first recorded cycling one running in 1897 from Rome to Naples (230km).
Is the Nove Colli the first Granfondo?
With thanks to Wikkipedia - Audax
Italian events and European climbs