If you happen to find yourself in Paris this September 20th and 21st, cancel all other plans, buy a copy of the newspaper, pack a good book, and prepare to stand in line for several hours.

'Are you crazy?' you might well be wondering. Why on earth would I be telling you to do such insane things in Paris, city of love, of light, of wonder and beauty? Because for these two days, you can gain unparalleled access to some of the greatest and most hidden treasures that Paris has to offer - for free.