From Wikipedia:
Exposition
The film shows an eight-minute drive through Paris in the early hours of the morning (05:30hrs), accompanied by sounds of a high-reving engine, gear changes and squealing tires. It starts in a tunnel of the Paris Périphérique at Porte Dauphine, with an onboard view from an unseen car exiting up on a ramp (and from there following this route) to Avenue Foch. Well-known landmarks such as the Arc de Triomphe, Opéra Garnier, and Place de la Concorde with its obelisk are passed, as well as the Champs-Élysées. Pedestrians are passed, pigeons sitting on the streets are scattered, red lights are ignored, one-way streets are driven up the wrong way, center lines are crossed, the car drives on the sidewalk to avoid a rubbish truck. The car is never seen as the camera seems to be attached below the front bumper (judging from the relative positions of other cars, the visible headlight beam and the final shot when the car is parked in front of a curb on Montmartre, with the famous Sacré Cœur Basilica behind, and out of shot). Here, the driver gets out and embraces a young blonde woman as bells ring in the background, with the famous backdrop of Paris.
Production
Shot in a single take, it is an example of cinéma-vérité. The length of the film was limited by the short capacity of the 1000 foot 35mm film reel, and filmed from a (supposedly) gyro-stabilised camera mounted on the bumper of a Mercedes-Benz 450SEL 6.9. A photo has surfaced that seems to reveal an Eclair cam-flex 35mm camera with a wide angle lens, and a typical "speed rail" hard mount - no gyros - on a Mercedes. This model, which could reach a top speed of 235 km/h (146 mph), was only available with a 3-speed automatic transmission. Yet, one can hear gear changes up into 5th, as well as heel-and-toe down-shifting with a high-revving engine indicating speeds of well over 200 km/h. Calculations made by several independent groups showed that the car never exceeded 140 km/h (85 mph). Lelouch himself claimed that the top speed achieved was somewhere between 230 km/h and 240 km/h. It is suggested that the soundtrack was dubbed with the sound of Lelouch's Ferrari 275GTB, which has a corresponding number of gears and a V-12 sound that is quite distinct from that of any V8, including the 6.9 liter V8 of the alleged Mercedes camera car.
A making-of-the-rendezvous documentary indicates that Lelouch himself was the driver, that the car driven was the Mercedes, although the sound track is from a Ferrari. One observer was posted, with a walkie talkie, close to the Louvre palace at the only blind junction (archway) to assist the driver. However, Lelouch has revealed that the radios failed, and if the assistant had tried to warn him of a pedestrian the message would not have been received.
Urban Legend
Due to the content of the film it has become somewhat infamous for rumors surrounding the making of it and its exposition. Upon release it was not known who was driving the car and rumors circulated that it was either an unnamed F1 racer, a taxi driver or Lelouch himself. The biggest rumor surrounding the film however, is that due to the illegal nature that had to be undertaken in order for the movie to be filmed, the director Claude Lelouch was arrested upon the first screening. It is unknown whether this is true.