The trial, which starts on Wednesday, will be held for security reasons in a specially adapted courthouse in Lamezia Terme in southern Italy, a city with historical links to the Calabrian mafia 'Ndranghetan.
A total of 355 people are accused in the trial, which is expected to last for several years.
A total of 900 witnesses will be heard.
The accused are suspected of, among other things, murder, drug trafficking, extortion and money laundering, crimes that date back as far as the 90s.
Brorson will testify against the "boss"
At the center of the trial is one of the most powerful families in 'Ndranghetan and its alleged leader, a 66-year-old man who goes by the nickname "Uncle".
One of the prosecutors' trump cards is that as many as 58 of the witnesses come from within the organization, people who have thus chosen to break the very foundations of the southern Italian mafia, the strict code of honor, loyalty and silence, omertá.
And one of these witnesses is a nephew of the suspected 66-year-old boss, who has now revealed the organization's secrets against a promise of police protection.
Controls cocaine trafficking
According to Chief Prosecutor Nicola Gratteri, Italy's most experienced and well-known mafia prosecutor, the 'Ndrangheta mafia, estimated to have around 20,000 members, has also spread far beyond Calabria's borders with interests in all parts of Italy, as well as in the rest of Europe and North America.
The group is estimated to have a turnover of around 50 billion euros a year and the main income comes from the equally lucrative and violent international cocaine trade, where 'Ndranghetan is believed to control large parts of the cocaine imported into Europe from South America.
"This trial shows how deeply rooted 'Ndranghetan' is in Italian society," Criminology professor Federico Varese at Oxford University told AFP.
However, he warns that the trial will in no way mean the end of the criminal group.
- You can throw them in jail, but if you do not correct the root cause of why they exist from the very beginning, they will only multiply.