Monaco Historic Grand Prix in Monte Carlo
The Monaco Historic Grand Prix sends vintage racing machinery back onto the same 3.3 kilometre Monte Carlo streets used by modern Formula 1, run by the Automobile Club de Monaco roughly two weeks before the main event. First staged in 1997 to mark the 700th anniversary of Grimaldi family rule, it was meant as a one-off but became a fixture on even years from 2000 onward, drawing period cars from Bugatti through Brabham.
The Monaco Historic Grand Prix exists because of an anniversary that was never meant to repeat itself.