Several reports. The controlled media are saying a few thousands, FromRome.Info has heard reports of upto 5 Million. Remember, these videos are from controlled media.
Ruptly covered the entire event live, here is a 11.5 hour long video
Here is a video by Moris San, an Italian freedom activist, who says there was 5 million. It shows a street filled with protesters to the horizon in both directions:
And here is another showing thousands protesting in the Mauritius Islands against the Corona Controls, also yesterday.