Gentlemen start your engines.
Tony’s travels to Monaco to take part in the Grand Prix. His hotel of choice is the the Hotel de Paris. Scenes of the racetrack and areas surrounding Monaco were filmed at this location and used for special effects background plates. Detailed film of the race course was able to be captured prior to the running of the actual race.
Roadway, Starting Grid, and Whiplash Fight
After running a lap in his Stark race car, Whiplash attacks Tony in front of the grandstands on the Route de la Piscine. The background plates and shots of the track all come from Monaco, shot before the Grand Prix began. Specific shots of Tony, Ivan, and any explosive effects in the fight were shot in a constructed set in Downey, California.
The attack on Tony’s car (and others) by Ivan Vanko, and all car explosions and stunts related to the big fight (including the attack on Happy and Pepper) was shot at the Downey Studios lot. This studio, which is no longer in existence, was created out of the former Rockwell International plant where NASA Space Shuttles and other vehicles were assembled. It is in no way related to Robert Downey, Jr.
(Iron Man 2, 2010)