You then take your 'passport' and start visiting the places listed, and in every place, there is a door/cupboard/closet/PO Box etc with a lock that fits your key.
In one place, you can turn on a street light (who often gets the opportunity to do that?)! In a museum you might get to see a secret exhibit.
I think this is such a great idea for locals and tourists alike to see little parts of the city that usually go unnoticed. I think more cities and even towns should embrace this fantabulous idea.
The full article is here: Art Installation in NY