Who is on trial?
As well as the Grand Hotel, Ms Veyrac also owns the La Réserve restaurant in Nice. The main suspect in the trial is the restaurant's former manager, Giuseppe Serena.
His contract was reportedly terminated by Ms Veyrac in 2009, and the 67-year-old is accused of ordering her abduction in order to obtain a €5m (£4.5m; $6.1m) ransom which he planned to use to open a new restaurant.
The Italian national is also accused of orchestrating an earlier attempt to kidnap Ms Veyrac in 2013.
Mr Serena, who has been in pre-trial custody for four years, is charged with complicity in kidnapping and attempted extortion as part of a gang. He denies the charges.
Philip Dutton, a former British soldier, is also among those charged. The 52-year-old from Liverpool was allegedly promised 10% of the ransom, according to investigators.
He has admitted involvement in the 2016 and 2013 kidnapping attempts. Enrico Fontanella, an Italian friend of Mr Serena, is also accused of involvement but he denies the charges.
All three men allegedly recruited local criminals to assist with the kidnapping plot.
Among the other defendants are private detective Luc Goursolas, who has admitted fitting a tracking device to Ms Veyrac's car but denies knowledge of the plan to abduct her.
Three suspected gang members from Nice, meanwhile, are accused of carrying out the kidnapping.