Paris, France - The opening ceremony for the Paris Olympics began Friday, an unprecedented and ambitious show with up to 7,000 athletes parading down the River Seine past the historic monuments of the French capital despite the risk of rain dampening spirits.

For the first time in Olympic history, the opening ceremony is taking place outside the main stadium, with some 300,000 people watching in person from specially built stands on the river banks, and another 200,000 from overlooking balconies and apartments.

As tradition dictates, the Greek delegation had the honor of leading out the flotilla, as the cradle of the modern Olympic movement.

In an ambitious, high-risk departure from past opening ceremonies, the athletes sailed down the river in an armada of 85 boats.

The show seeks to blend both French culture and history and the great Olympic moments of the past.

Despite the forecast of heavy rain and a wave of attacks that paralyzed France's high-speed rail network early Friday, organizers were confident of pulling off the audacious ceremony.

Chief Games organizer Tony Estanguet said before the show there would be some modifications if it was wet, but he insisted the weather would not dampen the mood.

"It's going to be a beautiful moment, it's going to be a great party," he added.

Pop icon Lady Gaga wowed the crowd of VIPS and spectators with an early performance in the ceremony.

Singers Ariana Grande and Pharrell were also called out by name in Instagram Stories on the official account of The Olympic Games, and Ari was spotted together with Wicked co-star Cynthia Erivo in their usual pink and green.

Basketball superstar LeBron James, who will be one of two Team USA flagbearers along with tennis star Coco Gauff, was seen being equipped with a clear plastic poncho to protect him from the predicted deluge just before the teams boarded the boats.

Around 3,000 dancers are performing from the banks of the river and monuments including Notre-Dame Cathedral in a show that will promote diversity, gender equality, and French history.