The Duel of Monaco was a failed attempt by Ivan Vanko to kill Tony Stark and avenge the death of his father Anton, who had been accused of espionage by Stark's father Howard.
Anton Vanko died in Moscow the day Tony Stark told the world he was Iron Man. That day Ivan Vanko, Anton's son, prepared to make his own armor, including an Arc Reactor in order to kill Stark.
He took a plane to Monaco six months later after getting the ticket from a Ten Rings Agent.
Stark and Pepper Potts travelled to Monte Carlo, Monaco. Knowing his death was imminent from Palladium poisoning, Stark decided to race his car in the Circuit de Monaco himself.